text stringlengths 1 1.11k | source dict |
|---|---|
java, game, swing, simon-says
/** Settings menu and submenus. */
JMenu settings = new JMenu("Settings");
JMenu colors = new JMenu("Choose Colors");
JMenuItem topLeft = new JMenuItem("Top Left");
JMenuItem topRight = new JMenuItem("Top Right");
JMenuItem bottomLeft = new JMenuItem("Bottom Left");
JMenuItem bottomRight = new JMenuItem("Bottom Right");
topLeft.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
changePanelColor("topLeft");
}
});
topRight.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
changePanelColor("topRight");
}
});
bottomLeft.addActionListener(new java.awt.event.ActionListener() { | {
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to this set the number 0, it simply returns a one type! F−1 are complex differentiable in z 0, we get the whole numbers it will be as... S Theorem to is 0 a complex number complex number that can hold the real component ( template! Numbers and compute other common values such as 2i+5 1+0i has this property and having unlimited precision, e.g unlimited... Same as x itself the justification is different than given + 0 * i, where x is part. Complex '' of just two parts: z = a + bi ) as +. Fractional part and an imaginary number values such as 2i+5 them to create a complex number than given returns! Zero, then 0 + bi can be pictured as an ordered pair of real numbers as! We add to this set the number 0, it is the square root, can. F/G one needs g ( z ) are real numbers part of Re z. Exponential form, into polar form to exponential form is real part: Re ( is 0 a complex number ) =.! Graphed on a complex coordinate plane modulus of a complex number degrees and π/2 is 90 degrees C++ that. X is | {
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"url": "https://marc-petit.com/h-agen-kqfbq/ca90fd-is-0-a-complex-number"
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ros, catkin-make, laser-scan-matcher
Original comments
Comment by MarkyMark2012 on 2016-03-21:
Cheers sir that has done the trick!! (Now it can't find csm header files - shall try and persuade it otherwise :) )
Comment by joq on 2016-03-21:
That should have resolved both header and library locations. What does pkg-config --cflags csm print?
Comment by MarkyMark2012 on 2016-03-21:
Comes back with -I/usr/include/cairo -I/home/pi/ros_ws/install/include
Comment by joq on 2016-03-21:
Seems OK. Are the headers in fact there?
Comment by MarkyMark2012 on 2016-03-21:
Just gotten around to checking this - so you were correct - the headers weren't there. Simply copied them into that dir and it's all complied! I now have - after some faff - LSM running on a Pi 2. Shall write all this up as a how-to...
Comment by joq on 2016-03-21:
Copying the headers should not have been necessary. The csm install should have created a csm.pc that points to the right place. If you write this up, try to figure out what when wrong with that. | {
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quantum-chemistry, hydrogen
In the H atom the equation is far more complicated but the general conditions imposed on the wavefunction remains the same; the imposition of boundary conditions, as determined by QM, results in the generation of integer quantum numbers so that theory matches experimental data. | {
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beginner, vba, excel
Title: Building an OPC client in Excel I am pretty deep into building a very multi-faceted little app in Excel with VBA. It does a number of tasks, all centered around using OPC to get tag values from several PLC's and doing various things with the info, like publishing a webpage (using a module I found, not mine), creating log files and tables and sounding some audible alarms for the office.
What I'm doing now is, upon a button push, connecting to the server (RSLinx), then entering a loop that first reads the tag values, then does each of the above tasks if the associated checkbox is checked. This will run fine indefinitely so long as the user doesn't screw with it or Linx or let the computer lock. | {
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special-relativity, group-theory, tensor-calculus, representation-theory, spinors
Title: If $v_{a \dot{b}}$ transforms like a four-vector, what does $v_{a}^{\dot{b}}$ describe? The $( \frac{1}{2}, 0)$ representation of the Lorentz group acts on left-chiral spinors $\chi_a$, the $( 0,\frac{1}{2} )$ representation on right-chiral spinors $\chi^{\dot a}$.
The $( \frac{1}{2}, \frac{1}{2}) = ( \frac{1}{2}, 0) \otimes ( 0,\frac{1}{2} ) $ representation acts therefore on objects with one dotted and one undotted index.
My naive, first guess would be that the $( \frac{1}{2}, \frac{1}{2}) $ representation acts on objects with one lower undotted and one upper dotted index: $v_{a}^{\dot{b}}$. An upper dotted index transforms like a right-chiral spinor, a lower undotted like a left-chiral spinor.
Quite surprising for me is that $v_{a \dot{b}}= v_\mu \sigma^\mu_{a \dot{b}}$ transforms like a four-vector and $v_{a}^{\dot{b}}$ transforms differently, because the transformation behaviour of a lower dotted index is different than that of an upper dotted index. | {
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of this fair coin. 1 Answer to A fair coin is tossed three times. The above explanation will help us to solve the problems on finding the probability of tossing three coins. A probability of zero means that an event is impossible. So, logically, the probability that he will get a head the first time is: 1/2 The second time he flips, the scenario's the same, and so with the third. While a run of five heads has a probability of 1 / 32 = 0. based on these results, what is the Two heads: 29 Two tails: 24 One head, One tail: 46 Answer the following questions based on the data you. the probability that you will get at least one head) = P(1) + P(2) + P(3) = 3/8 + 3/8 + 1/8 = 7/8. What is the probability of getting (i) all heads, (ii) two heads, (iii) at least one head, (iv) at least two heads? Sol. Expected Tosses for Consecutive Heads with a Fair Coin Date: 06/29/2004 at 23:35:35 From: Adrian Subject: Coin Toss What is the expected number of times a person must toss a fair coin to get 2 | {
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"url": "http://ylpw.flcgorizia.it/a-coin-is-tossed-three-times-what-is-the-probability-of-getting-3-heads.html"
} |
you can repr. Image data are usually given on homogeneous point lattices, e. The area of the 1st BZ is the area of the primitive cell in the reciprocal latt. are the elementary (or primitive) direct lattice vectors. But the problem of how to construct a FHE scheme had been bothering cryptologists since it was initially introduced by Rivest et al. b) The general reciprocal lattice vector G k 1 b 1 k 2 b 2 k 3 b 3. , b be defined as above. Periodic stacking of balls, producing a 3-dimensional network (direct lattice). The positions of the lattice points are defined by the lattice vectors a and b. primitive unit cell. The primitive cell is a parallelepiped specified by the primitive translation vectors. Partial Occupation tools. The crystal system of the reciprocal lattice is the same as the direct lattice (for example, cubic remains cubic), but the Bravais lattice may be different (e. Issendor 17. find the a primitive cell for this lattice and write down its unit vectors. The smallest of | {
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python, beginner, python-3.x, homework
class zip(object)
| zip(iter1 [,iter2 [...]]) --> zip object
|
| Return a zip object whose .__next__() method returns a tuple where
| the i-th element comes from the i-th iterable argument. The .__next__()
| method continues until the shortest iterable in the argument sequence
| is exhausted and then it raises StopIteration.
|
| Methods defined here:
|
| __getattribute__(self, name, /)
| Return getattr(self, name).
|
| __iter__(self, /)
| Implement iter(self).
|
| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
|
| __next__(self, /)
| Implement next(self).
|
| __reduce__(...)
| Return state information for pickling.
>>> help(sum)
Help on built-in function sum in module builtins:
sum(...)
sum(iterable[, start]) -> value | {
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decoherence, foundations
The "measurement limit" is the limit in which the decoherence in one observable's eigenbasis is so rapid and so complete that competing terms don't have a chance. This is the defining feature of a perfect measurement. Natural measurements, like the mutual "measurements" incurred by the molecules in a macroscopic sample of gas, are far enough away from being perfect that both position and momentum can be approximately well-defined (without violating the uncertainty principle $\Delta x\Delta p\gtrsim\hbar$, of course). | {
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condensed-matter, topological-order, topological-insulators
gap (and without breaking certain symmetry). Simply generalize this to the many-body case, we may say that the topologically ordered states are called "topological" because they can not be smoothly connected to the trivial product state without closing the many-body gap. | {
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ros, pcl, sicklms
/home/karthik/ros_workspace/pcs200/src/pcs200.cpp:17: error: ‘const struct sensor_msgs::PointCloud2_<std::allocator<void> >’ has no member named ‘points’
/home/karthik/ros_workspace/pcs200/src/pcs200.cpp:17: error: ‘const struct sensor_msgs::PointCloud2_<std::allocator<void> >’ has no member named ‘points’
/home/karthik/ros_workspace/pcs200/src/pcs200.cpp:17: error: ‘const struct sensor_msgs::PointCloud2_<std::allocator<void> >’ has no member named ‘points’
/home/karthik/ros_workspace/pcs200/src/pcs200.cpp:17: error: ‘const struct sensor_msgs::PointCloud2_<std::allocator<void> >’ has no member named ‘points’
/home/karthik/ros_workspace/pcs200/src/pcs200.cpp:17: error: ‘const struct sensor_msgs::PointCloud2_<std::allocator<void> >’ has no member named ‘points’
/home/karthik/ros_workspace/pcs200/src/pcs200.cpp:17: error: ‘const struct sensor_msgs::PointCloud2_<std::allocator<void> >’ has no member named ‘points’ | {
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gravity, biophysics, biology, scaling
\begin{align}
m g &= 0.5 \rho C_D V^2 \frac{S_{\rm human}}{144} \\
\therefore \frac{m_{\rm human}}{1728} g &= 0.5 \rho C_D V^2 \frac{S_{\rm human}}{144} \\
\therefore V^2 &= \frac{144}{1728} \frac{2~m_{\rm human}~g}{\rho C_D S_{\rm human}} \\
V^2 &= \frac{1}{12} V_{\rm human}^2 \\
\therefore V &= 0.2887 V_{\rm human}
\end{align}
These rough calculations show the terminal velocity of a borrower would be about 29% that of a human (29% of 200 km/h = 58 km/hr) , which is still pretty darn fast (ask the insects that die on your windshield when you're driving on a highway). | {
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python, ai, neural-network
Output fields:
. Name - 17 chrs
. Transform Function - 24 chrs
. Training Strategy - 3 chrs (P - train after each pattern, E - train after each epoch)
. Learning Epsilon - 7 chrs
. Learning Acceleration - 7 chrs
. Training Results - 3 chrs (E - error, F - failed, T - trained)
. Number of epochs trained.
"""
name,tf,tp,le,la = scenario
f.write('{:17s}{:24s}{:3s}{:<7,.4g}{:<7,.4g}{:3s}{:<4,d}\n'.format(name, tf.__name__, tp, le, la, self.decipher_training_result(trained), len(self.epochs)))
def write_details(self, scenario, trained, f):
"""
Display the results of a training session with tabular detail. | {
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parsers, ambiguity
Title: Parse forest from an ambiguous grammar Parser-generators like nearleyjs can return a parse forest instead of a parse tree.
Since not all input may result in a parse forest (eg, the input may exercise only a non-ambiguous subset of the grammar), how do you programmatically choose the 'correct' parse tree from the forest?
One option is to always choose the first element from the array of parse-trees returned.
Another option is to flag the returning of a parse-forest (instead of a single tree) as an error. But then, this would defy the whole point of having Earley-like parsers that allow parsing of ambiguous grammars! | {
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• Do you think this problem is NP-hard? I'm not convinced it doesn't have a poly time solution, and the ILP solvers are unlikely to finish even moderately sized instances.
– R B
Feb 1, 2015 at 9:51
• @RB, I have no idea whether it is NP-hard. See my comment under the question about dynamic programming for my first thought about how to try to find a polynomial-time algorithm (but I don't know if the resulting algorithm will be in P or not). As far as what ILP solvers can do, the only way to find out is to try -- sometimes their performance can be surprising.
– D.W.
Feb 1, 2015 at 18:17 | {
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discrete-signals
Title: Confusion regarding discrete signal value? I know that discrete signals have finite precision. But does that means that those signals can have only integer values(for example,2,3,4 etc) but not decimal values(for example 2.1,3.2,4.2 etc)? There might be a confusion in the discreteness.
It can apply to the ordinal variable of the data: time for signals, space for images. Here discrete is the opposite of continuous. Which is not often well-defined. A common way is to consider that samples are finite in quantity, or enumerable: you can index them in $\mathbb{Z}$. For irregularly-sampled signal, we are in a borderline case.
For instance, a classically discrete signal $x[n]$, $n\in\mathbb{Z}$ is considered discrete (in time).
But their values (the quantities attached to $x[n]$) might be continuous in nature, e.g. $\mathbb{R}$. This is generally the context of the standard linear signal processing processing (because quantization is typically non-linear). | {
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javascript, jquery, node.js, ecmascript-6, socket.io
/**
* Route raw input to the correct channel.
* @param {Object} chat - The applicable chat application
*/
const processUserInput = chat => {
const message = $userMessageInputField.val()
if (isCommand(message)) {
const systemMessage = chat.processCommand(message)
if (systemMessage) {
$roomMessages.append(divSystemContentElement(systemMessage))
}
}
else {
chat.sendMessage($roomNameHeader.text(), message)
$roomMessages.append(divEscapedContentElement(nickName + ': ' + message))
$roomMessages.scrollTop($roomMessages.prop('scrollHeight'))
}
$userMessageInputField.val('')
}
/**
* Detect whether the given raw input is a command.
* @param {string} message - The raw input
* @returns {boolean} - Whether the raw input is considered a command
*/
const isCommand = message => {
return message.charAt(0) === '/'
} | {
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javascript, performance, game, random
Title: Adding an 'enemy' to a game (with randomized properties) I'm working on a game using the now abandoned Famo.us Javascript framework.
I have the game in a running prototype and I'm building with Cordova and running it on an iPhone 6 using PhoneGap.
There seems to be some performance issues with it and I can't help but notice that a bit of lag happens right as a new enemy is generated onto the field.
There's a few random factors when generating a new enemy:
position on the screen
type of enemy
direction of travel | {
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ros-humble, hardware-interface, diff-drive-controller, ros2-control
robot_controller_spawner = Node(
package="controller_manager",
executable="spawner",
arguments=["hoverboard_base_controller", "--controller-manager", "/controller_manager"],
)
# Delay rviz start after `joint_state_broadcaster`
#delay_rviz_after_joint_state_broadcaster_spawner = RegisterEventHandler(
# event_handler=OnProcessExit(
# target_action=joint_state_broadcaster_spawner,
# on_exit=[rviz_node],
# )
#)
# Delay start of robot_controller after `joint_state_broadcaster`
delay_robot_controller_spawner_after_joint_state_broadcaster_spawner = RegisterEventHandler(
event_handler=OnProcessExit(
target_action=joint_state_broadcaster_spawner,
on_exit=[robot_controller_spawner],
)
) | {
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c#, entity-framework, asp.net-web-api
As @Disappointed commented, if there is nothing in parallel, there is no reason to use async/await.
Now, to your questions:
Where should I put this validation? Should it be in the controller?
It is usually a good idea to separate your business logic from everything else, so changes on it does't spread throught all your application. So, the validation should be on your business layer. The controller gets the data from the repository, send it to the appropriate class on the business layer, which execute the rules on that data, and return the results to the controller.
Should I create a separate class for validation and use it in controller?
Yes, as per answer 1.
How should i return potential validation errors to the front end? Should it be an exception with a message? | {
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function in circuits. The Farad, F, is the SI unit for capacitance, and from the definition of capacitance is seen to be equal to a Coulomb/Volt. Dielectric constant Parallel plate capacitor C K C air d A C K o =. Capacitors • Capacitance of a parallel – plate capacitor (in air). A parallel plate capacitor of area A, plate separation d and capacitance C is filled with three different dielectric materials asked May 21, 2019 in Physics by Ruksar ( 68. A capacitor is an electrical device designed for storing electric charge, generally consisting of two parallel conducting plates separated by an insulating layer called a dielectric. 3 Capacitor symbols. Parallel-plate Capacitor formula: C = K ε 0 A/d where: ε 0: 8. The capacitance of a. Capacitance Example No1. Parallel Plate Capacitor. 85 ×10-12F/m. 1 DeÞnition of Capacitance 26. These are our plates. Let the parallel plate capacitor be filled with two blocks of identical size and dielectric constants k_1=3. The space between their plates | {
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java, object-oriented, file-system
}
/*
* {@link pp5_7.Bookshelf} instance that holds each {@link pp5_7.Book}
*/
private static Bookshelf shelf = new Bookshelf();
/*
* Creates the main menu prompt message and prompts the user for which
* option to proceed.
*
* @return Menu option selected
* @see pp5_7.Prompt
*/
private static int mainMenu() {
String prompt = "\n"
+ "\t1. Add a book\n"
+ "\t2. Remove a book\n"
+ "\t3. Browse\n"
+ "\t4. Empty bookshelf\n"
+ "\t5. Save bookshelf\n"
+ "\t6. Load bookshelf\n"
+ "\t7. Quit\n"
+ "Please select an option";
return Prompt.intInRange(prompt, 1, Main_Options.QUIT.ordinal() + 1,
"Not a valid option.");
} | {
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As has already been pointed out, $P(\alpha)$ makes a jump at every rational number. With the approach outlined above, one can in principle compute both the "lower" and "upper" values of $P(\alpha)$ (the upper value being the probability that $S_n$ reaches, but does not cross, the line of slope $\alpha$) whenever $\alpha$ is rational. This is feasible only when $\alpha$ is a relatively simple fraction, but it should still be possible to obtain a good plot of $P(\alpha)$ as a function of $\alpha$.
I recall that after this problem was discussed at the open problem session of FPSAC 2003, Pontus von Brömssen made some such plots. I haven't been in touch with him in the last few years, but apparently he has an (inactive) MO-account. I will notify him of this question. | {
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"url": "https://mathoverflow.net/questions/63789/probability-of-a-random-walk-crossing-a-straight-line"
} |
time-series, random-forest, xgboost
I would go with 1 with you have very limited time, little problem knowledge and the problem is not too critical. 2 looks more promising with you can play with the feature engineering and knows something about the problem process (or has access to someone who does). If limited time, little problem knowledge and model performance is critical, I would try some neural network approach. | {
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• Side note: I though this was about phasors, since the solution is essentially an exponentially decaying phasor... whose magnitude decreases as it spins around the complex plane? As for why they must be complex conjugates, I am not sure, does it have something to do with the fact that one needs to cancel the other out based on initial conditions? Sep 7, 2016 at 22:36 | {
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"url": "https://electronics.stackexchange.com/questions/256662/where-did-j-go-in-the-underdamped-response-of-an-rlc-circuit"
} |
java
public Criativo setFormato(String formato) {
this.formato = formato;
return this;
}
public String getCanal() {
return this.canal;
}
public Criativo setCanal(String canal) {
this.canal = canal;
return this;
}
public List<Arquivo> getArquivos() {
return this.arquivos;
}
public Criativo setArquivos(List<Arquivo> arquivos) {
this.arquivos = arquivos;
return this;
}
public String getNome() {
return this.nome;
}
public Criativo setNome(String nome) {
this.nome = nome;
return this;
}
public Criativo addArquivo(Arquivo arq) {
this.arquivos.add(arq);
return this;
}
public String getId() {
return this.id;
}
public Criativo setId(String id) {
this.id = id;
return this;
}
public String getValidacaoId() {
return this.validacaoId;
} | {
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} |
complexity-theory, np-complete, strings, permutations
If we restrict the problem to instances with $|w_i|\le k$ (where $k$ is a fixed constant), we obtain a new problem $WT_k$. $WT_k$ belongs to $P$. It's possible to build a polynomial-time algorithm for $WT_k$, using dynamic programming. Indeed, in this case the number of different words $w_i$ is bounded by $2^k$. Hence any sequence $\{w_1,\ldots,w_n\}$ can be encoded by a $2^k$-tuple of integers (an element of $\mathbb{Z}^{2^k}$). It is convenient to assume that $w_i\ne \varepsilon$. | {
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"tags": "complexity-theory, np-complete, strings, permutations",
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} |
rotational-dynamics, rotation
I'm guessing that the notion of pressure and shear force is the most mysterious to you. The way we measure the way dollops of fluid interact with their neighbors is through the stress tensor. This is a slightly frightening word, but bear with me. You are to imagine a small polyhedron of fluid and we wish to calculate the forces on the faces from the neighboring fluid. You specify the face by a vector pointing in a direction normal to the face and whose length is proportional to the face's area. Then the tensor is a matrix - a linear function - that takes this vector and returns another vector - the force on the face. You multiply the face vector by the matrix to get the force.
In general, you probably know that matrices change the directions of the vectors they multiply. The component of force in the direction of the face vector, i.e. normal to the face, is called the pressure; that along the face's plane is called the shear. | {
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Responding to Henry, June 6, 2011, this equivalence emerges from a simple experiment given by Hugo Steinhaus in 'Mathematical Snapshots'. Take a roll of something (I use paper towelling) and saw through it obliquely, thus producing elliptic sections. Unroll it and you have a sine curve. (Tom Apostol and Mamikon Mnatsakanian suggest you rest a paint roller at an angle in the paint tray. Then paint!)
Paul Stephenson May 8 '13 at 21.00
-
On MATLAB:
$$t = 0:0.001:(2\pi);$$ $$st = \sin(t);$$
$$\text{sum( sqrt( diff(st).^2 + diff(t).^2 ) )}$$
$$\text{ans} = 7.6401$$
You will need $21.6$% more paint to paint the corrugated roof ;).
- | {
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"openwebmath_score": 0.8723611831665039,
"tags": null,
"url": "http://math.stackexchange.com/questions/45089/what-is-the-length-of-a-sine-wave-from-0-to-2-pi/45092"
} |
java, optimization, recursion, chess
Iterating over all squares for isAllBeenOn() is cumbersome. I suggest using a Set<Position> to keep track of all visited positions. (Hence the need for Position to implement .equals() and .hashCode().)
.setDegree() and .getDegree() are awkwardly named — especially since the former sounds like it operates on a scalar quantity. More appropriate names would be .initDegreesOfFreedom() and .getDegreesOfFreedom().
The conditions in setDegree() look nasty. In fact, it's wrong, because you hard-coded 6 as a magic number instead of varying it according to the board size. There are a number of ways to fix that, the most elegant being to reuse the possibleMoves() routine. I think that this bug demonstrates the wisdom of preferring maintainability over performance — and the performance impact is minimal anyway.
Algorithm
This line in Solver.solve() looks particularly nasty: | {
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slam, localization, navigation, mapping, 2d-mapping
Title: Can I localize with imprecise/noisy sonar sensor?
I have a small differential drive robot with a single sonar sensor mounted on the front of it. I also have an IMU and GPS on the vehicle. My goal is to navigate from one point to another in an unknown environment and avoid obstacles along the way.
At the moment we're testing indoors, so the GPS is out of the picture. I want to be able to send a waypoint via rviz (simulating a GPS coordinate waypoint) and have the vehicle navigate there.
I don't believe mapping is necessary for my application, however I think localization is - or else how would it know it arrived at its destination? I plan on using robot localization to combine my IMU and odometry sensors and create a pose estimate. But won't that estimate drift over time? | {
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• @Hans. Your answer is wrong, because you start from a false identity. The trace of $\sqrt{VU^TUV^T}$ is not equal to that of $\sqrt{U^TU}\,\sqrt{V^TV}$ in general, it is only larger. Your mistake comes from the fact that square root does not behave well under product. Consider the case where $V=D>0$ is diagonal and set $S=\sqrt{U^TU}$. Then $A:=SD$ is diagonalisable with real eigenvalues and arbitrary otherwise. You are comparing the traces of $\sqrt{A^TA}$ and that of $A$. The first one is obviously larger. Apr 18, 2018 at 6:37 | {
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"openwebmath_score": 0.9227038025856018,
"tags": null,
"url": "https://mathoverflow.net/questions/297953/nuclear-norm-as-minimum-of-frobenius-norm-product"
} |
c++, error-handling, linux, library, socket
native_socket_t create_socket ( Protocol p, Type t ) throw ( SystemException );
void close_socket ( native_socket_t socket ) noexcept;
bool poll ( native_socket_t socket, PollType type, const std::chrono::milliseconds &wait_time ) throw ( SystemException );
/**
*@return number of bytes read.
*@param[in] remove if not set later calles to read on same socket will return same data
*/
unsigned int read ( native_socket_t socket, byte_buffer &buffer, const unsigned int length, bool remove )
throw ( SystemException, RemoteHungUpException );
/**
*@return number of bytes written.
*/
unsigned int write ( native_socket_t socket, const byte_buffer &buffer ) throw ( SystemException, RemoteHungUpException,
BufferTooLargeException ); | {
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"tags": "c++, error-handling, linux, library, socket",
"url": null
} |
black-holes, event-horizon
Do they have a model of what goes on inside the event horizon? If so, how does any "resonant sloshing" of mass (or whatever) inside of the new event horizon show up in this "ring down" tail of the gravity wave resulting from the merger? The event horizon is not a very useful concept in a highly dynamical numerical simulation. It is defined as the boundary of the region that cannot send signals to infinity, so by definition nothing comes out during merger (or at any other time). But this means that to find the event horizon you actually have to know the complete evolution of the spacetime (i.e. finish the numerical simulation). Sometimes this is done (numerically) so that pretty pictures can be drawn, but there isn't too much physics in it since the pictures depend on arbitrary embeddings (choices of coordinates) anyway. | {
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"url": null
} |
javascript, beginner, html, event-handling, firebase
let divider = document.createElement('option');
divider.text = "--------------------";
divider.disabled = true;
accountLists[i].add(divider);
for(let j = 0; j < listOfAccountNames.length; j++) {
let newOption = document.createElement('option');
newOption.text = listOfAccountNames[j];
newOption.value = listOfAccountNames[j];
accountLists[i].add(newOption);
}
} | {
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"tags": "javascript, beginner, html, event-handling, firebase",
"url": null
} |
In addition to the cartesian and polar forms of a complex number there is a third form in which a complex number may be written - the exponential form. Subset sum. So we're multiplying 6 by itself eight times. Listed as the first operand is a value properly in the range from no less than 1. You can use both positive and negative exponents. The name of the new command, which must begin with a \, is the name you'll use in the document to use the command. Scientific notation in LaTex? Hi, im engineering student therefore using allot of scientific notations. Matrix and Element-wise Operations. 5f will keep 5 digits after the decimal point, including trailing zeros. function , latex. In in-line math mode, we use$ signs to enclose the math we want to display, and it displays in-line with our text. Collaborators who are not online will be notified about new messages the next time they sign in. I am not mathematically inclined but I have to read papers containing maths quite a lot of the time. | {
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"openwebmath_score": 0.8853237628936768,
"tags": null,
"url": "http://bjwg.sicituradastra.it/latex-exponential-notation.html"
} |
general-relativity, black-holes, wormholes
Title: Why I cannot cross the Einstein-Rosen bridge? I have been told that no observer can ever cross the wormhole present in the Kruskal-Szekeres coordinates, connecting region 1 and 4 in the Kruskal-Szekeres diagram, usually called Einstein-Rosen bridge. The reason given is that, in order to cross the wormhole from region to 1 to 4 or vice-versa, the trajectory of the observer would have to be spacelike somewhere. | {
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because (a) the Euclidean distance is easier to compute and interpret than the Mahalanobis distance; because (b) the greater difficulties of computing the variance-covariance matrix required by the Mahalanobis distance measure, when the variance-covariance matrix is. Therefore, distance metrics, unlike actual measurements, can be directly used in spatial analytical modeling. Or another example where MOV A, #08H ---> result A=70H. when objects represented by sensory measurements or by structural descriptions are compared. This approach can be equiv-alently interpreted as a linear transformation of the origi-nal inputs, followed by Euclidean distance in the. distance, it weights the Euclidean distance by the covariance matrix (think of Euclidean distance as weighing the distance by the Identity matrix). Transformation Types The inverse of is a Mahalanobis distance metric. All pixels are classified to the nearest class unless a standard deviation or distance threshold is specified, in | {
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"openwebmath_score": 0.776372492313385,
"tags": null,
"url": "http://chet.pontevecchioparquet.it/mahalanobis-distance-vs-euclidean-distance.html"
} |
.net, security, validation, f#
Pretty simple, and definitely keeps things more functional.
In the same respect, I did all the other boolean if statements the same way.
The only weird one was the passed one in main:
[<EntryPoint>]
let main argv =
let tests : ITests list = [new StreamingPinTests(); new ListManipulationTests()]
let runTest(test:ITests) =
let result = test.RunAll()
match result with
| true ->
Console.ForegroundColor <- ConsoleColor.White
printfn "Test %s ran %i passed." test.Name test.TestCount
| false ->
Console.ForegroundColor <- ConsoleColor.Red
printfn "Test %s ran %i failed." test.Name test.TestCount
result
let passed =
tests
|> List.where (fun x -> x |> runTest)
|> List.length
Console.ForegroundColor <- ConsoleColor.White
printfn "All tests ran." | {
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c++, roman-numerals
class Roman_int {
public:
Roman_int() = default;
explicit Roman_int(const Integer& value)
:integer{ value }, roman{ integer_to_roman(value) }
{
}
explicit Roman_int(const Roman& value)
:integer{ roman_to_integer(value) }, roman{ value }
{
}
Roman as_roman() const { return roman; }
Integer as_integer()const { return integer; }
private:
struct Roman_integer_values {
Roman_integer_values(const Roman_value& roman_digit, const Integer_value& integer_digit)
:roman{ roman_digit }, integer{ integer_digit }
{
};
Roman_value roman;
Integer_value integer;
};
using Lockup_table = std::vector<Roman_integer_values>;
static const Lockup_table lookup_table;
Roman roman{};
Integer integer{}; | {
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wavefunction, quantum-optics, software, quantum-states
Just noticed in my code I have the hyperbolic functions with argument $r/2$ but you have $r$ so be mindful of that... sorry. | {
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} |
parasitology
There are many claims on the internet (and printed works) expounding on how simple it is to drown fleas. The best science I found so far on the topic is in Forensic Entomology: An Introduction By Dorothy Gennard; John Wiley & Sons, Apr 30, 2013; section 4.3 which reflects a 1985 work by Simpson K. (Journal of the New York Entomological Society 76: 253-265, not finding this online). Gennard is using the fleas present on a human body at death to determine how long the body had been submerged. Findings - | {
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"url": null
} |
javascript, snake-game, webgl
//========================
// Apple
//========================
function Apple(){
this.pos = Location(2,1,2)
}
Apple.prototype.move = function(){
// Set the location to a random x and z.
var x = randomNumberBetween(2,38)
var z = randomNumberBetween(-8,28)
this.pos = Location(x,1,z)
if(randomNumberBetween(1,11)===1&&score>15){
apple.type="superapple"
} else {
apple.type="apple"
}
}
Apple.prototype.draw = function() {
var sphere
// Generate a new sphere.
if(this.type=="superapple") {
sphere = new newMesh( applegeometry, superapplematerial );
} else {
sphere = new newMesh( applegeometry, applematerial );
}
// Get the data location.
var applepos=apple.pos | {
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"tags": "javascript, snake-game, webgl",
"url": null
} |
java, random, io, generator
ArrayList<String> draft1 = new ArrayList<>();
draft1.addAll(nbaDraft1.createDraft(draftOrder, draftPlayers));
// create ArrayList to hold draft info (teams in proper order associated w/ players they drafted)
// nbaDraft1.printDraft(draft1); // print draft (Un-comment code in order to print draft instead of
// reading from text file to be created below)
CreateDraftFile draft = new CreateDraftFile();
// create object of class w/ methods to write and read file that'll hold your particular draft
draft.writeToFile(draft1); // call method to write your draft to a text file
System.out.println();
draft.readDraftFile(); // call method read and print the info on file
}
}
public class NbaDraft {
private ArrayList<String> list;
private ArrayList<String> order;
private ArrayList<String> picks;
private ArrayList<String> draft;
private String rounds;
private int numRounds; | {
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gravity, forces, spacetime, education
Are there other (or additional) metaphors that might be helpful in illustrating to lay readers (a) what motivates modern gravitational theory and (b) why it has greater explanatory power than Newtonian gravitation? The best way to understand curved space-time is Einstein's way in 1907. Imagine all of space is filled with clocks which are held in place, but they need tick at different rates in order to stay simultaneous with each other. Near a massive object, the clocks tick slowly, away from masses, they tick faster.
Particles travel through space so that they locally take the path of maximum time between fixed endpoints, so that between endpoints which are close to a massive object, their path curves out a little, meaning that they are bent toward the massive object.
This is a statement of the Einstein 1907 theory of gravity, which he knew then would be the weak field, slow velocity approximation to Genera Relativity. It is counterintuitive for a few reasons: | {
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coffeescript, comparative-review
Of course, this doesn't mean that you should extract every less-than-trivial boolean condition to a helper function. Where you draw the line may be different from person to person. The fact that you're asking this question seems to suggest that you're inclined to make this move. (Personally I would extract it too.) | {
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species-identification, entomology, wasps
Title: What is this wasp? We live in central New York and these large (1.25") wasps are invading our house pretty regularly. I want to say it's a great black wasp, but the pale yellow striping makes me wonder.
A sample specimen
Edit
Confirmed the answer: these have all been female Northern Paper Wasps: | {
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java, performance, algorithm, combinatorics, minesweeper
Solution.java: (135 lines, 3778 bytes)
/**
* Represents a solution for a Minesweeper analyze.
*
* @author Simon Forsberg
* @param <T>
*/
public class Solution<T> {
public static <T> Solution<T> createSolution(GroupValues<T> values) {
return new Solution<T>(values).nCrPerform();
}
private static <T> double nCr(Entry<FieldGroup<T>, Integer> rule) {
return Combinatorics.nCr(rule.getKey().size(), rule.getValue());
}
private double mapTotal;
private double nCrValue;
private final GroupValues<T> setGroupValues;
private Solution(GroupValues<T> values) {
this.setGroupValues = values;
} | {
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newtonian-mechanics, harmonic-oscillator, spring, equilibrium
Title: Equilibrium position for double spring hanging vertically I feel a bit daft asking this but how do you calculate the equilibrium position of a system with a spring (spring constant k1) hanging from the ceiling with a mass (m1) attached to the bottom, and attached to m1, there is another spring with spring constant k2 which is attached at the bottom to a mass m2.
I know how to calculate the motion with the Lagrangian and Newtonian approach, but I wish to know how to calculate the extension of the spring in equilibrium position given the spring constants and masses. | {
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ros, python, script, deb
Title: How can I generate deb installable file from the python files in my ROS package (script folder)?
Hello Everyone,
How can I generate deb installable file from the python files in my package(in the script folder), so I can deliver the deb file to the client who can run the python executables in the package?
For example, I just completed the ROS tutorial and created the beginner_tutorials package in my catkin workspace. I also completed the Simple Publisher and Subscriber tutorials which mean the python talker.py and listener.py in the script folder in the beginner_tutorials package.Then I run the following command in the package folder,~/ROS/catkin_workspace/src/beginner_tutorials:
$ bloom-generate rosdebian --os-name ubuntu --ros-distro kinetic
$ fakeroot debian/rules binary
So it generated the deb file. After I installed the deb to a new machine and I try to run the command:
$ rosrun beginner_tutorials talker
$ rosrun beginner_tutorials talker.py | {
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electromagnetic-radiation, climate-science
Title: Why do CO₂ and other greenhouse gases interact with infrared radiation but not ultraviolet wavelengths? When ultraviolet and visible wavelength photons get sent from the sun they seem to not interact with CO₂ and other greenhouse gases. When that electromagnetic energy gets to the earth, the earth radiates energy back out in the form of infrared radiation which does interact with greenhouse gases causing those gas molecules to vibrate which causes some of this energy to be sent back to earth.
My question is why does smaller wavelength radiation not interact with CO₂ but larger wavelengths do? | {
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homework-and-exercises, classical-mechanics, kinematics, rotational-kinematics
In K, B is steady (velocity $\v vB=0$) and A's velocity is
$$\v vA = \v\om{}\times\v rA$$
always tangent to the circle. There are two positions of A where $\v vA$
directly points to B: the one drawn, where A is approaching B, and that
symmetric wrt CB, where A is receding from B.
In K$'$, $\v vA'=0$ whereas
$$\v vB' = -\v\om{} \times \v rB.$$
This is on a straight line from B orthogonal to CB and never touches
the circumference. Then B's velocity is never directed towards
A. The right drawing shows that: B's velocity has a component towards
A, of $1\,\rm m\,s^{-1}$, but this is not the full velocity of B as seen
from K$'$ frame. It's drawn as the downward $2\,\rm m\,s^{-1}$ vector.
This has nothing to do with A's location.
Edit
In order to better understand the meaning of both components of $\v
vB'$ let's decompose $\v rB$ in eq. (1):
$$\v rB = \ora{\rm CA} + \ora{\rm AB}.$$
Then
$$\v vB' = -\v\om{} \times \ora{CA} - \v\om{} \times \ora{AB}.\tag2$$ | {
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finite-impulse-response, polyphase
Title: 16x interpolation using polyphase FIR - sum of the coefficients I have an issue with polyphase implementation during interpolation. Lets assume I have 256 taps long FIR lowpass sinc filter. In order to interpolate by a factor of 2 I do use two FIR filters (polyphase filter) out of the main one since I don't need to calculate zero stuffed samples. The same goes with interpolation by a factor of 4 in which case four sub-filters (polyphase filters) are used. | {
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# Difference between revisions of "2017 AMC 12B Problems/Problem 25"
## Problem
A set of $n$ people participate in an online video basketball tournament. Each person may be a member of any number of $5$-player teams, but no two teams may have exactly the same $5$ members. The site statistics show a curious fact: The average, over all subsets of size $9$ of the set of $n$ participants, of the number of complete teams whose members are among those $9$ people is equal to the reciprocal of the average, over all subsets of size $8$ of the set of $n$ participants, of the number of complete teams whose members are among those $8$ people. How many values $n$, $9\leq n\leq 2017$, can be the number of participants?
$\textbf{(A) } 477 \qquad \textbf{(B) } 482 \qquad \textbf{(C) } 487 \qquad \textbf{(D) } 557 \qquad \textbf{(E) } 562$
## Solution
Solution by Pieater314159
Minor edits by Zeric | {
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building-design, pneumatic, engineering-history
This seems surprising. Why set up an air compressor system and run pneumatic tubes through the walls? Wouldn't an electric system be easier to set up and maintain?
What were the factors that made pneumatic thermostats so popular? In the 1940's and 50's, dynamic system controllers were invented which used air pressure to work. It was possible in fact to design and build not only analog control mechanisms but also binary logic devices that ran on compressed air and which could perform simple switching functions. These devices were less expensive and more durable than electronic logic based on vacuum tubes and relays and were popular all the way up into the early 1970's. They were called "pneumatic logic" or "air control" and they disappeared quickly when solid state logic became cheap. | {
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logic, natural-deduction
By the way, in case you're interested: one reason this inference is difficult to solve is that not all logicians agree with it! There are logicians who proposed something called "Free Logic", with the main idea being that it is possible for no objects to exist at all. If no objects exist at all, then $S \to \exists x Q(x)$ might be true (it will be true if $S$ is false), but $\exists x (S \to Q(x))$ is definitely false no matter what, because there does not exist any $x$ period. | {
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javascript, html5, optimization
function onFileWrite=function(e) {
finishedRequest(filename); //filename needs to be retrieved from somewhere...
if (onSuccess!==undefined) onSuccess(filename);
}
I guess that your intention was to define a function for each case and then assign it.
So your example transforms into this (I'm just reorganizing your code and fixing a function declaration).
var onFileWrite = function(e) {
finishedRequest(filename); //filename needs to be retrieved from somewhere...
if (onSuccess!==undefined) onSuccess(filename);
}
...
fileWriter.onwriteend=onFileWrite;
... | {
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ros
Comment by 215 on 2015-05-01:
Ok... i narrowed it down into being something with the way i am converting.. because as soon it gets set it terminates.
Comment by Adam Allevato on 2015-05-01:
Try to launch the talker using rosrun, so you can see its output in the terminal. Start adding printout statements to ensure that your program gets to each line, beginning at the very start of the program.
Comment by 215 on 2015-05-01:
It seems to terminate when the variable is set from the vector...
Comment by Adam Allevato on 2015-05-01:
You call multiple vectors in your code. What line causes the crash?
Comment by 215 on 2015-05-02:
it crashes at line 93.
This looks like a question that's more appropriate for StackOverflow - it's a general programming issue. | {
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frequency-spectrum, time-series, math, integration, notation
There are also more exotic measures that are not absolutely continuous with respect to the Lebesgue measure.
I have found no evidence of the notion of absolute continuity of stochastic measures.
EDIT: While theoretical results about spectral representations of WSS processes are crucial for applications, the $dZ$ notation may be off-putting and perhaps even doubt-inducing. I suspect that writing $Y(\omega)d\omega$ for $dZ(\omega)$ is a useful abuse of notation that allows the user to manipulate symbols as though some analogue of the Radon-Nikodym derivative existed. Rigor can be added after the fact.
Note that rigor might arrive decades after the fact. Plenty of ideas seem to work just fine without complete mathematical rigor. | {
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ros, navigation, message, performance
Originally posted by abarral on ROS Answers with karma: 138 on 2012-02-20
Post score: 1
I'm pretty sure there isn't a map ROI package available yet. (See edit at end of this post)
I have a half-finished node that converts the map to an image and publishes it using image_transport. This has the advantage that one can use the compressed (jpg) or theora compression options which save huge amounts of bandwidth. Of course these compression schemes are lossy, but for visualization they're ok. For additional bandwidth saving, the node publishes a full and/or a tile based image, the latter showing only the victinty of the robot pose. This way, the map around the robot can be visualized using only a few kb/s of bandwidth.
Another node running on the GUI side could reassemble the image to maps, so they can be visualized in rviz as usual. Haven't done this yet, but should only take time :)
Let me know if you want to take a look at it (it's not in our public repo for a reason though :) ). | {
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botany, plant-physiology, plant-anatomy
Title: Why are newly grown leaves red? After a period of heavy rain, several trees in my garden will put out an impressive burst of new leaves, with an incredible vibrant red colour, almost the colour of port wine. The new leaves will then slowly turn green.
I understand that the leaves turn green once they start producing chloroplasts and chlorophyll, but what is responsible for this initial red colour that is so very vibrant? And what biological role does it play? It is anthocyanins that are produced to protect the developing photosystems (chlorophylls) from being damaged by sunlight. | {
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$$\sum_{k=0}^{L} 4^k = \frac{4^{L+1}-1}{4-1} = \frac{4}{3} \frac{4^{L}-1/4}{1}$$ This corresponds to having added all numbers $b_i$ from $i=1$ up to $i=2^{2L+1} -1 = 2 \cdot 4^L - 1$. Since we are continuing adding zeroes until $i=2^{2(L+1)} -1 = 4 \cdot 4^L - 1$, the value of the sum won't change. Since the OP's question asks for the mean, we have that the mean oscillates between $$\frac{4}{3} \frac{4^{L}-1/4}{2 \cdot 4^L - 1}$$ and $$\frac{4}{3} \frac{4^{L}-1/4}{4 \cdot 4^L - 1}$$
Large $n$ is the same as large $L$, so taking $L\to \infty$, the mean oscillates between $2/3$ and $1/3$, hence the limit does not exist.
• (+1) I like this sequence and the computation of the means is good, too. – robjohn Jul 25 '17 at 18:07 | {
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gravity, angular-momentum, simulations, galaxies, particle-physics
As you probably already guessed this is not enough to make it form a flat disc. I've been reading about galaxies and found that the cause of the disc shape is because angular momentum is hard to get rid of. However, angular momentum is not really a separate law right? I mean, by using the attraction by the inverse square of the radius the angular momentum should be constant? Please, correct me if I'm wrong.
So what am I missing? Dark matter? Dissertation? I realize that galaxy formation is a REALLY broad and advanced topic but my simulation is ONLY to get particles to form a disc shape.
Any help appreciated! You get a disk when the particles lose energy (often by radiating it away) but keep their angular momentum.
Galaxies are made of stars, but the stars are born from clouds of gas. The gas has many ways to radiate energy away, which can cause it to settle into a disk. The stars may then be formed in the disk structure. | {
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ros-kinetic, ros-indigo
I figured out that the .msg file on the robot has one line missing, which is present on the .msg file on my pc. This results in the md5 hash to be different. So I tried deleting the line in the .msg file on my pc and "catkin build" my package.
This would be one way to work-around the version difference, but note that this leads to a difficult situation: you should rebuild all packages that use this message to make sure that no (de)serialisation issues crop up. From the description in your question, I guess that won't be possible.
Disregarding that, for now it would probably make sense to try and figure out why rosmsg md5 .. seems to not pick up the edited version of your file. Where did you actually "delete the line in the .msg file"? In a package in your Catkin workspace, or in /opt/ros/kinetic/..?
Originally posted by gvdhoorn with karma: 86574 on 2019-03-20
This answer was ACCEPTED on the original site
Post score: 0 | {
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bond, ionic-compounds, transition-metals, covalent-compounds
In the case of pyrite we have a relatively hard cation, with a small ionic radius and charge of +2, and a rather large anion, with a charge of -2. Therefore there will be a significant degree of covalent character in the Fe-S bonds due to the polarising effect of the cation on the anion. This is confirmed by experimental results and theoretical calculations which suggest that the charge on Fe is about +2/3 and the charge on S is about -1/3. This is significantly less than the expected charges of +2 and -1 from a purely ionic model and so indicates that there is significant sharing of electrons. This is supported by measurements and calculations of the electron density, which show significant electron density between the atoms.
Reference: http://pubs.rsc.org/en/content/articlepdf/2014/sc/c3sc52977k | {
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observational-astronomy, astrophysics, spectroscopy
The other end of the fiber optic cable provides input light for the echelle spectrograph. You can read more about how the spectrograph works by reading my answer that I linked above.
My friend aimed his telescope at the moon, which was about hall full and almost directly overhead, and made sure we stayed on it. The next photo is the color echellogram we obtained:
and here is the same photo in grayscale: | {
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performance, c, parsing, chess
<Fullmove counter> ::= <digit19> {<digit>}
<digit19> ::= '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
<digit> ::= '0' | <digit19>
Also, since this is part of a chess engine, the position representation must be small for cache performance, and the operations like moving pieces, getting castling rights, etc, must be fast because the position is modified in a recursive function that searches for the best next move.
Here's the code for pos.c:
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <check.h>
#include "pos.h" | {
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r, bioconductor, biomart, refseq
Title: Get RefSeq accession numbers with versions Google searching for NM_002084 gives the following result:
NM_002084.4
This, I assume, is the latest version v4, hence the .4 suffix.
Searching for previous versions I get the following results, along with notes saying it was updated or removed.
NM_002084.3
This sequence has been updated. See current version.
NM_002084.2
NM_002084.1
Record removed. This record was replaced or removed.
Using biomaRt I can get the latest(?) version as follows:
library("biomaRt")
# define db
ensembl <- useMart("ensembl", dataset = "hsapiens_gene_ensembl") | {
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c++, algorithm, vectors
Title: Compressing a vector into a specific range I want to solve the following task --- I am given a vector of integers. I want to 'compress' this list, where the elements will be replaced with numbers 0 through n - 1, where n is the number of unique elements in the vector, such that the relative ordering among the elements is preserved, i.e., if previously vector[index1] < vector[index2], then that is still true after the compression. In other words, each element is replaced with its ranking among the source vector.
For example, given the vector {1, 3, 10, 6, 3, 12}, the elements will be replaced with 0 through 4 since there are 5 unique value. To preserve ordering, it will be transformed into {0, 1, 3, 2, 1, 4}.
Right now, to complete this, I use the following algorithm:
#include <iostream>
#include <map>
#include <set>
#include <vector>
using namespace std; | {
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javascript, strings, programming-challenge, array, ecmascript-6
const getAllConsecutiveStrings = (strArr, numStr, arrLen) => {
const numConsecStr = arrLen - numStr
const result = []
let consecStr
for (let i = 0; i <= numConsecStr; i++) {
consecStr = ""
for (let s = i; s < i + numStr; s++) {
consecStr += strArr[s]
}
result.push(consecStr)
}
return result
}
const getFirstLongestString = strArr => {
let firstlongestString = ""
let longestLength = 0
for (let str of strArr) {
strLen = str.length
if (strLen > longestLength) {
firstlongestString = str
longestLength = strLen
}
}
return firstlongestString
} Some performance-related nitpicking:
Instead of string concatenation keep an array of string lengths;
Use a running window of current concatenated length: when advancing to the next string simply subtract the first window's element and add the current string length. | {
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cosmology, big-bang, cosmological-inflation, galaxies
As far as the effects of this time delay on viewing the rotation of the galaxy, the length of the cosmic year (the length of time it takes for the sun to travel around the center of the Milky Way) is 225 to 250 million years. So, as many other people have already pointed out, the rotation period of a galaxy is small compared to the time it takes for light to travel across the galaxy and there is no jumbling effect. | {
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"tags": "cosmology, big-bang, cosmological-inflation, galaxies",
"url": null
} |
civil-engineering, retaining-wall
Weep hole
Perforated drain pipe
Surface water diversion
Dewatering wells | {
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} |
haskell, physics
We expect the first argument always to be some kind of time measurement. We also expect the vector to be conform to the time's unit(*). From this point of view, it makes sense to encode the Time in D. However, this yields the question why the other side of the spacetime, space, isn't encoded in D too.
(*) strictly speaking, we're not encoding time's unit but only type.
Either way, you probably want to allow only Time values. Furthermore, you want to make clear what unit Time uses. We could use a phantom type, e.g.
{-# LANGUAGE DataKinds, KindSignatures, GeneralizedNumtypeDeriving #-}
data TimeUnit = Milliseconds | Seconds | Minutes | Hours
newtype Time (* :: TimeUnit) a = Time {fromTime :: a} deriving (Show, Num) | {
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ros, ros-release, release
Title: "ERROR: Stack's declared dependencies are missing calculated dependencies"
I run this command: rosrun release create.py wu_ros_tools 0.1.0 electric
using the electric version of the release script.
The stack file I'm using is here in my repository.
However, after the above command checks out the repo, I get this error.
ERROR: Stack's declared dependencies are missing calculated dependencies:
geometry
visualization
diagnostics_monitors
common_msgs
...but I DID declare those stacks, didn't I?
Originally posted by David Lu on ROS Answers with karma: 10932 on 2012-09-13
Post score: 0
Might there be local changes in your working copy?
Originally posted by tfoote with karma: 58457 on 2012-09-14
This answer was ACCEPTED on the original site
Post score: 0
Original comments
Comment by David Lu on 2012-09-16:
Must've just de-synched. Works now. | {
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} |
the distance between two points. Euclidean distance measures the straight-line distance between two points. It has been shown that when the number of eigenvectors is relatively high, the Mahalanobis distance outperforms the other measures. work on distance (e. 1 Mahalanobis distances The basic Euclidean distance treats each variable as equally important in calculating the distance. But estimation of a covariance matrix requires an exceptionally large sample size, which grows geometrically as more variables are considered. [3] J K Ghosh and P P Majumdar, Mahalanobis, Prasanta. Figure 1 illustrates two clus-ters, one obtained using Euclidean distance and the other obtained by Mahalanobis distance. It is similar to maximum likelihood. Euclidean-to-AffGrassmannian Point to Affine Subspace [Vincent et al. Bhattacharyya Distance. It is effectively a multivariate equivalent of the Euclidean distance. Learn Math Tutorials Bookstore http://amzn. z P>|z| [95% Conf. When raw data is provided, the | {
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"id": null,
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"url": "http://chet.pontevecchioparquet.it/mahalanobis-distance-vs-euclidean-distance.html"
} |
c++, performance, parsing
template <std::size_t RHS_SIZE, std::size_t LA_SIZE>
template <std::size_t FIRST_SIZE>
std::vector<const char*> LR1Item<RHS_SIZE, LA_SIZE>::first_of(
std::unordered_map<const char*, std::array<const char*, FIRST_SIZE>> first_sets) {
if (parsed_till + 1 <= rhs.size() - 1) {
std::vector<const char*> first = get_following_items(first_sets);
// if we find ε ("" in this case) in the first set
if (std::find(first.begin(), first.end(), "") != first.end()) {
if (parsed_till + 1 > rhs.size() - 1) {
// add all the lookahead symbols
first.reserve(lookahead.size());
for (const char* la: lookahead) {
first.push_back(la);
}
}
}
// remove ε ("" in this case)
std::remove(first.begin(), first.end(), "");
return first;
} else {
// if we are a final item, just return a vector version
// of the lookahead | {
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} |
java, design-patterns, mvc, swing
public Color getColor()
{
return color;
}
public void setColor(Color color)
{
this.color = color;
}
}
View part:
public class MainFrame extends JFrame
{
private TopMenu menuBar;
private DrawPanel drawPanel;
private ToolsMenu toolsMenu;
public MainFrame(Model model) throws HeadlessException
{
super("Paint Application");
prepareFrame();
initializeToolsMenuComponents();
initializeTopMenuComponents();
drawPanel = new DrawPanel();
JPanel mainLayoutforApplication = new JPanel(new BorderLayout());
mainLayoutforApplication.add(toolsMenu, BorderLayout.WEST);
mainLayoutforApplication.add(drawPanel, BorderLayout.CENTER);
this.add(mainLayoutforApplication);
} | {
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"tags": "java, design-patterns, mvc, swing",
"url": null
} |
algorithms, algorithm-analysis
An algorithm that counts the number of containing pairs
Here is an algorithm that counts the number of containing pairs between two given sets of non-wrapping ranges, $\mathcal N$ and $\overline{\mathcal W}$. It is, basically, sweep-line technique together with Fenwick tree. | {
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rospy
While providing the file parameter as a command line argument, it says No such file or directory. Below is the output of terminal -
ravi@ravi-pc:~/ros_ws$ roslaunch kinematics baxter.launch file:=src/../../Desktop/joint_states.csv
File "/home/ravi/ros_ws/src/kinematics/src/trajectory.py", line 19, in __init__
with open(file_name, 'r') as f:
IOError: [Errno 2] No such file or directory: 'src/../../Desktop/joint_states.csv'
ravi@ravi-pc:~/ros_ws$ ll src/../../Desktop/joint_states.csv
-rw-rw-r-- 1 ravi ravi 179308 May 19 20:46 src/../../Desktop/joint_states.csv
ravi@ravi-pc:~/ros_ws$ roslaunch kinematics baxter.launch file:=src/kinematics/sample/joint_states.csv
File "/home/ravi/ros_ws/src/kinematics/src/trajectory.py", line 19, in __init__
with open(file_name, 'r') as f:
IOError: [Errno 2] No such file or directory: 'src/kinematics/sample/joint_states.csv'
ravi@ravi-pc:~/ros_ws$ ll src/kinematics/sample/joint_states.csv | {
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} |
c++, c++11, parsing
expr += tok;
} else {
s += tok;
}
tok = "";
} else if (tok == "+" or tok == "-" or tok == "*" or tok == "/" or tok == "(" or tok == ")") {
if (state == 0) {
expr += tok;
is_expr = 1;
tok = "";
n = "";
}
} else if (tok == "=" and state == 0) {
if (lex_tokens.back() == "eq") {
if (condstarted == false) {
lex_tokens.back() = "eqeq";
} else {
condition += "eqeq ";
lex_tokens.pop_back();
}
} else {
lex_tokens.push_back("eq");
}
tok = "";
} else if (tok == reserved[12] and state == 0) {
if (condstarted == false) {
lex_tokens.push_back("and");
} else {
condition += "and ";
}
tok = "";
} else if (tok == reserved[13] and state == 0) {
if (condstarted == false) { | {
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"openwebmath_score": null,
"tags": "c++, c++11, parsing",
"url": null
} |
Little math problem(s) May 2021
04-30-2021, 08:54 PM
Post: #1
pier4r Senior Member Posts: 2,075 Joined: Nov 2014
Little math problem(s) May 2021
I wanted to leave one little problem as usual, hopefully it won't be too trivial but neither too overwhelming.
This is one among of the shortest math publications
Anyway they didn't provide the code through which they found the result (although one can suspect they optimized it a bit, despite the CDC6600 being a beast at the time).
Thus the task would be to write a code, for a calculator, that finds the counterexample in an optimized way (as otherwise the search space can blow up), of course aside from hardcoding or nearly hardcoding the counterexample.
---------------- | {
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"url": "https://www.hpmuseum.org/forum/thread-16845-post-147465.html#pid147465"
} |
homework-and-exercises, newtonian-mechanics, harmonic-oscillator, spring, coupled-oscillators
\frac{i e^{i t \sqrt{\omega_{1}^{2} + \omega_{2}^{2}}}}{2 \left(\omega_{1}^{2} + \omega_{2}^{2}\right)^{\frac{3}{2}}}\\\frac{e^{- i t \sqrt{\omega_{1}^{2} + \omega_{2}^{2}}}}{2 \left(\omega_{1}^{2} + \omega_{2}^{2}\right)} & - \frac{i e^{- i t \sqrt{\omega_{1}^{2} + \omega_{2}^{2}}}}{2 \left(\omega_{1}^{2} + \omega_{2}^{2}\right)^{\frac{3}{2}}} & - \frac{e^{- i t \sqrt{\omega_{1}^{2} + \omega_{2}^{2}}}}{2 \left(\omega_{1}^{2} + \omega_{2}^{2}\right)} & \frac{i e^{- i t \sqrt{\omega_{1}^{2} + \omega_{2}^{2}}}}{2 \left(\omega_{1}^{2} + \omega_{2}^{2}\right)^{\frac{3}{2}}}\end{matrix}\right].$$ | {
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} |
dataset, text-mining, nlp, text-classification
It's rare to have a perfect dataset, so realistically in my opinion the first issue is probably acceptable because the noise in the labels should be very limited. The second issue could be a bit more serious but this depends on what is the end application. Keep in mind that a trained model is meant to be applied to the same kind of data as it was trained/tested on. | {
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"url": null
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electrostatics, charge, capacitance
Do we see sparks? Or is it some current flow? Or something else?
Say I have a charged sphere, so where will the charge go on charge leaking? (Assuming that it is has an electric field less than the breakdown strength of the medium) Leakage of charge in capacitors can have different reasons in practice. Charges may escape into an imperfect insulator, or flow through the insulator as a tiny current. Charges may also escape via surface conduction on the capacitor itself or on the PCB it is mounted on. The charged sphere in air may lose charge via surface conduction of its support, or even via charging air molecules or neutralizing ions present in the air. Very thin insulators may allow for small currents between capacitor plates due to quantum tunneling. Depending on the exact mechanism and measurement method, discharging could be seen as discrete events (e.g. of single charge escape) or as a steady continuous process. | {
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# Given an anti-chain of the powerset of a finite set, is there a disjoint maximal chain?
Denote by $$X^{(r)}$$ the subset of $$\mathcal{P}(X)$$ such that every element has cardinality $$r$$ where $$1 \leq r \leq n = |X|$$
Suppose we have an antichain $$\mathcal{A}$$ of the partial ordering of $$\mathcal{P}(X)$$ by inclusion, that is not of the form $$X^{(r)}$$ for some $$r$$. Must there exist then a maximal chain that is disjoint from $$\mathcal{A}$$?
I am very stuck on this, however I suspect that it is true. I have a two ideas of how one might go about showing this that I can't seem to complete:
For contraposition, we supposed that for an antichain $$\mathcal{A}$$ we do not have any maximal chains that are disjoint from it. We want to show that $$\mathcal{A}$$ is then $$X^{(r)}$$ for some $$r$$. | {
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"url": "https://math.stackexchange.com/questions/2973741/given-an-anti-chain-of-the-powerset-of-a-finite-set-is-there-a-disjoint-maximal"
} |
quantum-mechanics, operators, angular-momentum, momentum
Title: What is momentum in a quantum sense? I’m currently taking my first course in quantum mechanics, and was looking over my notes on wavefunctions of particles with definite momentum.
Suppose $\psi=Ce^{ikx}$, we know from DeBroglie that this particle has a definite momentum because it has a definite wavelength.
We can calculate the expectation value of $p$ by evaluating $$⟨p⟩_{\psi}=\int_{-\infty}^{\infty}\mathrm{d}x\ \psi^*(x)\hat{p} \ \psi (x).$$
That being said, is this momentum the same as in classical mechanics, or is this a different physical quantity? In the "classical limit" $\hbar \rightarrow 0$, quantum mechanics reproduces the predictions of classical physics.
The exact definition of momentum is the one you gave. In the classical limit, this quantity behaves exactly the same way as the classical momentum behaves in classical mechanics. Outside of the classical limit, it behaves differently (and in a way that agrees with experiment). | {
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quantum-field-theory, symmetry, noethers-theorem, classical-field-theory
$$
\hat\phi'\equiv\mathrm e^{i\theta\hat Q}\hat\phi\mathrm e^{-i\theta\hat Q}\equiv \mathrm e^{i\theta Q}\hat\phi
$$
where $Q\in\mathbb R$ is a scalar. The generator of this symmetry is $\hat U(\theta)=\mathrm e^{i\theta\hat Q}$. The infinitesimal change in $\phi$ is
$$
\theta\delta\hat\phi=[\hat Q,\hat\phi]=iQ\phi
$$
The conserved charge is
$$
\hat Q=\int \hat j^0(\textbf{x},t) d^D\textbf{x}=iQ\int d^D\textbf{x}[(\partial_0\hat\phi)\hat\phi^*-(\partial_0\hat\phi^*)\hat\phi].
$$
Sometimes some authors drop the factor of $Q$ in the definition of $\hat Q$, so that the infinitesimal change in $\phi$ reads
$$
\theta\delta\hat \phi=i\phi
$$ | {
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newtonian-mechanics, reference-frames, coordinate-systems, vectors, units
Example 2.
Basis vectors often have unit length. If they don't have unit length they would introduce annoying scaling factors and we don't want that. An interesting example is the Frenet-Serret frame. This frame is used for parametric curves and it defines a basis based on the tangent vector and its normals.
Given some curve $\vec x(t)$ in 3D space we can calculate its tangent vector by normalizing the velocity $$\vec T(t)=\frac{\vec x'(t)}{|x'(t)|}$$. We can then form a normal vector from the tangent by repeating this procedure once more $$\vec N(t)=\frac{\vec T'(t)}{|T'(t)|}$$
One can proof that this vector is perpendicular to $\vec T$ because it has a constant length. Finally we can construct the final basis vector by taking the cross product of these two $\vec B=\vec T\times \vec N$. Each of these vectors has unit length so we have a nice basis. | {
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} |
physical-chemistry, safety
Given this, why does liquid oxygen not condense when you leave an open dewer of liquid nitrogen out? I mean, the air touching the surface of the nitrogen on top of the trap is the same as the air pumping through it. Is there too much nitrogen evaporating for the air to get close, or is the surface of the nitrogen too warm, or some other reasons? If you look at the vapour pressure graph for oxygen you’ll see that at its partial pressure in air, it can only liquefy below about 77 K, which by coincidence is the temperature of boiling liquid nitrogen. The air immediately above the liquid nitrogen / air interface cannot be any colder than that 77 K (slightly less, because nitrogen is only 4/5ths of the air), so the 1/5th that is oxygen cannot actually condense – it doesn’t get cold enough. Adding to that is the fact that the evaporating nitrogen further dilutes the oxygen that is present, further lowering the temperature that would be needed to condense oxygen at that pressure. | {
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} |
organic-chemistry, inorganic-chemistry, nitro-compounds
I guess I do understand that Ag compound, regardless of which one it is would not entirely dissociate as is the case with AgCN group. Hence, whichever atom is bonded to Ag, the R group would be attached to the other atom that is available. that is... if Ag is attached to N, RONO would be formed whereas if Ag is attached to O, RNO2 would be formed. KNO2 confuses me a little too. Since there is a complete dissociation, we have the NO2- group. In this case, would it be the Nitrogen atom that would attach to the R group (since it is less electronegative and would thus donate electrons more easily) or would it be the Oxygen atom that would attach (since it simply has more available electrons to form bonds)? In other words, for KNO2 or KONO, whichever one it is, would the product be RONO or RNO2? The reference[1] mentioned in the comments shows that the reaction of silver nitrite with alkyl halides produces predominantly the nitro compound, $\ce{R–NO2}$ with over $80$% yield. This suggests | {
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"tags": "organic-chemistry, inorganic-chemistry, nitro-compounds",
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} |
lua, complex-numbers
function Complex:__sub(other)
return self:__add(- other);
end
function Complex:__mul(other)
if type(other) == "number" then
return Complex:new(
self.r * other,
self.i * other
)
else
return Complex:new(
self.r * other.r - self.i * other.i,
self.i * other.r + self.r * other.i
)
end
end
function Complex:__eq(other)
return
self.r == other.r and
self.i == other.i
end
function Complex:__lt(other)
-- incorrect but for sorting
if self.r == other.r then
return self.i < other.i
else
return self.r < other.r
end
end
function Complex:tostring(i)
if type(i) ~= "string" then
i = "i"
end | {
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"tags": "lua, complex-numbers",
"url": null
} |
navigation, navsat-transform-node, phidgets, navsat-transform, robot-localization
Originally posted by blasalat on ROS Answers with karma: 51 on 2017-10-25
Post score: 0
It's not so much that you need the offset; you just need an earth-referenced heading. The yaw_offset and magnetic_declination parameters are there to allow you to compensate for the fact that (a) most magnetometers read 0 at north, not east, and (b) they read 0 at magnetic north, not true north.
So you could just calculate that heading from course over ground and generate a sensor_msgs/Imu message that navsat_transform_node would listen to instead of your actual IMU message. Just make sure it conforms to standards: a heading of 0 means you are moving directly east, and turning left is positive rotation. I would imagine course over ground assumes 0 at north, so you can either manually adjust for that in your course-over-ground-heading-node, or you can set yaw_offset to pi/2.
Originally posted by Tom Moore with karma: 13689 on 2018-01-24
This answer was ACCEPTED on the original site
Post score: 1 | {
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} |
python, datetime, unit-testing
Title: Simple greeting program based with timezone offset I made a simple set of functions that returns a greeting based on the current time, the user's timezone offset, and the user's level. For context I wrote this as a part of a larger chat bot application. I am not sure if there is a better way to handle the if/elif/else blocks in both functions.
Please let me know of places of improvement.
"""A module for creating greeting strings based on a user's timezone
offset and user's level."""
import time
def get_part_of_day(user_tz_offset, time_now):
"""Return part of day depending on time_now and the user's timzone
offset value.
user_tz_offset - integer of user's time zone offset in hours
time_now - UTC time in seconds | {
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will de ne a function f 1: B !A as follows. Let f: A → B. Proof. Yes. The above problem guarantees that the inverse map of an isomorphism is again a homomorphism, and hence isomorphism. The range of a function is all actual output values. I've got so far: Bijective = 1-1 and onto. If we fill in -2 and 2 both give the same output, namely 4. In mathematics, a bijective function or bijection is a function f : A → B that is both an injection and a surjection. The function f: ℝ2-> ℝ2 is defined by f(x,y)=(2x+3y,x+2y). A function f (from set A to B) is bijective if, for every y in B, there is exactly one x in A such that f(x) = y. Alternatively, f is bijective if it is a one-to-one correspondence between those sets, in other words both injective and surjective. Show that f is bijective and find its inverse. Let’s define $f \colon X \to Y$ to be a continuous, bijective function such that $X,Y \in \mathbb R$. it doesn't explicitly say this inverse is also bijective (although it turns out that | {
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c++, beginner, game, console, rock-paper-scissors
goto playagain;
}
else {
cout << "i couldn't understand could u repeat please?" << endl;
goto playagain;
}
}
} Welcome to Code Review and welcome to C++! Let's go through the code and see what can be improved.
In C++, the headers of the form <xxx.h> are deprecated, which means they should not be used. You are recommended to use
#include <ctime>
instead of #include <time.h>.
using namespace std; is considered bad practice because it causes name clashes. It will cause problems when you try to use common identifiers like size, count, find, etc. See Why is using namespace std; considered bad practice?. Explicitly qualify the names with std:: instead. You will find that this makes the code more readable when you deal with larger programs and multiple libraries.
I notice that your code structure looks like this:
#include <iostream>
#include <string>
#include <time.h> | {
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python, file-system
def compare_text_docx_pdf(path):
#List containing all file names + their extension in path directory
myDir = os.listdir(path)
#List containing all file names without their extension (see splitext doc)
l = [splitext(filename)[0] for filename in myDir]
#Count occurences
a = dict(Counter(l))
#Print files name that have same name and different extension
for k,v in a.items():
if v > 1:
print(k) | {
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matrix elements. Assuming that v1 and v2 are in the XZ plane, then the direction of the cross product vector will point upwards if the rotation from v1 to v2 is counter clockwise, and downwards if the rotation is clockwise. By using dot() method which is available in the geometry library one can do so. Coronavirus illustrations new 404 error illustrations popular Welcome illustrations popular Education illustrations Business illustrations. A vector quantity has two characteristics, a magnitude and a direction. A dot product is defined as the sum of the products of the corresponding entries of the two arrays. Python Program. To compute the dot product 2. “Multiply” two vectors when only perpendicular cross-terms make a contribution (such as finding torque). The only difference is that in dot product we can have scalar values as well. The dot product is a float value equal to the magnitudes of the two vectors multiplied together and then multiplied by the cosine of the angle between | {
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"url": "http://sabrinamanin.it/c-program-to-find-dot-product-of-two-vectors.html"
} |
ros, pcl, pcl-ros, tf-conversions, transform
Originally posted by Eric Perko with karma: 8406 on 2012-07-01
This answer was ACCEPTED on the original site
Post score: 3
Original comments
Comment by jodafo on 2012-07-01:
Works, thank you.
Comment by bzr on 2014-12-02:
The Eigen Geometry Module Tutorial no longer exists. Is there an updated version? | {
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= sin(nx). Graphs of Other Trigonometric Functions. Similarities. LA Times - October 27, 2019. It directly determines. Just copy and paste the below code to your webpage where you want to display this calculator. are simple modifications of the Sine- and Cosine function whose properties (amplitude and frequency) shall be recognized in the graphs. In a formula, it is written simply as 'cos'. We will be studying rational polynomial functions later in the course. Use a Pythagorean Identity to get in terms of cosine. Drag a point along the cosine curve and see the corresponding angle on the unit circle. The sine and cosine functions are also commonly used to model periodic function phenomena such as sound and light waves, the position and velocity of harmonic oscillators, sunlight intensity and day length, and average temperature variations through the year. Start at the point , which lies on the unit circle centered at the origin. 12/11/2018; 2 minutes to read +1; In this article. The | {
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"url": "http://tuningfly.it/ikjw/cosine-function.html"
} |
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