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Question: <p>What are some incapabilities that the earlier spectroscopy (Visible, Ultraviolet and Infra-red) have when compared to the more modern method?</p>
Answer: <p>Some of the things that come to mind are:</p>
<ul>
<li><strong>Resolution</strong> Modern equipment has much higher resolution than older equipment... | https://chemistry.stackexchange.com/questions/11039/what-are-some-incapabilities-that-the-early-spectroscopy-have-when-compared-to-t |
Question: <p>I'm trying to find a reason for an experimental observation, I noticed that when the absorbance of $\ce{Ca}$ is measured with FAS(flame atomic spectroscopy) that it decreases when metals such as $\ce{Al}$ and $\ce{K}$ is present(the ions). I used a $\ce{Ca}$ hallow cathode lamp. </p>
<p>Any idea as to why... | https://chemistry.stackexchange.com/questions/16327/why-does-the-absorbance-of-ca-decrease-in-the-presence-of-certain-metals |
Question: <p>Typically the antisymmetric stretch in IR spectroscopy is higher than the symmetric stretch for a given functional group. For example for $\ce{NO2}$ the antisymmetric stretch falls at $\sim 1530\ \mathrm{cm^{-1}}$ compared to $1350\ \mathrm{cm^{-1}}$ for the symmetric stretch. Likewise $\ce{NH2}$ has a sim... | https://chemistry.stackexchange.com/questions/19562/assign-symmetric-and-antisymmetric-stetches-in-ir-spectroscopy |
Question: <p>I ordered a DIY spectroscopy kit from public-lab, however don't have access to a halogen lamp to calibrate the wavelengths.</p>
<p>I'm wondering if it would somehow be possible to calibrate the wavelength using the iPhone camera light?</p>
Answer: <p>According to the <a href="http://publiclab.org/wiki/sp... | https://chemistry.stackexchange.com/questions/24969/wavelength-of-iphone-4s-camera-light-for-visible-spectroscopy-calibration |
Question: <p>can anyone tell me the difference between absorption spectroscopy and extinction spectroscopy in terms of experiment? and how to get extinction spectroscopy, how to get absorption spectroscopy? Thank you so much.</p>
Answer: <p>There should not be any difference in experiment, because the extinction is so... | https://chemistry.stackexchange.com/questions/33187/difference-between-absorption-spectroscopy-and-extinction-spectroscopy |
Question: <p>I have done a geometry optimization of <em>cis</em> and <em>trans</em>-difluoroethene using RHF/STO-3G in Gaussian03. Although this is a simple method and a small basis set, this should ideally put place the molecule in a minimum on its potential energy curve. Within this minimum are vibrational states. I ... | https://chemistry.stackexchange.com/questions/40481/observe-from-ir-raman-spectra-whether-molecule-is-in-a-local-minimum-on-pes |
Question: <p>A typical data processing step for acquired absorption/transmission data is normalizing, i.e. stretching the curve such that it is bounded between 0 and 100%.</p>
<p>However, the absorption/transmission curve changes with the density and thickness of the sample. Moreover, absorption is a non linear phenom... | https://chemistry.stackexchange.com/questions/42441/why-absorption-transmission-spectroscopic-data-is-normalized |
Question: <p>I need to calculate the spectral overlap integral for the emission spectrum of coumarin 334 and the absorption spectrum for rhodamine, using spreadsheets (MS Excel).</p>
<p>Following the theory of Fluorescence Resonance Energy Transfer (Förster), I have the definition of the spectral overlap integral:</p>... | https://chemistry.stackexchange.com/questions/44376/how-to-calculate-spectral-overlap-integral-using-spreadsheets |
Question: <p>I am to show that the number of absorbed photons only is proportional to the optical density at <em>low optical densities.</em></p>
<p>I do not know how to do this, but this reminds me of the linear range of absorbance vs concentration; at high concentrations, the relationships is no longer linear. I also... | https://chemistry.stackexchange.com/questions/44666/proportionality-between-number-of-absorbed-photons-and-optical-density |
Question: <p>Why is it that lighter atoms are more likely to produce Auger emission and the heavier atoms fluorescence in x-ray spectroscopy? It doesn't make any sense. Lighter atoms should try to resist double ionization, plus there are fewer electrons around which means there is a lesser chance of a photon hitting an... | https://chemistry.stackexchange.com/questions/46529/auger-emission-probability |
Question: <p>Through EPR measurements it is possible to gain information about the spin states of molecules. So a singlet state will give no signal/only noise and a molecule with unpaired electrons will result in an EPR spectrum.</p>
<p>What happens if a measured sample would contain a mixture of singlet and triplet s... | https://chemistry.stackexchange.com/questions/46572/epr-spectrum-of-a-singlet-triplet-mixture |
Question: <p>I know you can use GC-MS for the analysis of gaseous molecules, but would you be able to instead use an infrared spectroscopy method to analyse gaseous molecules, or does it need to be mass spectroscopy?</p>
Answer: <p>GC-MS is just one common method of what is known as '<a href="https://en.wikipedia.org/... | https://chemistry.stackexchange.com/questions/48022/changing-the-spectroscopy-type-to-infrared-in-gc-ms |
Question: <p>My lecturer said 462 nm is infrared region. I think the wavelength is visible light. Which region is the correct one? I need confirmation about this one.</p>
Answer: <p><a href="https://i.sstatic.net/ibV3r.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ibV3r.png" alt="enter image descripti... | https://chemistry.stackexchange.com/questions/58403/what-is-the-region-of-this-wavelength-462-nm |
Question: <p>I understand the basic concepts of the photoelectron spectrum. However, say I am instructed to draw the PES graph for Silicon. I know how to figure out the relative peaks based on its configuration. But when arranging them on the graph, how can I accurately place them where they should be in ionization ene... | https://chemistry.stackexchange.com/questions/60423/how-to-draw-a-photoelectron-spectrum-with-ionization-energies |
Question: <p>I am trying to get some bearing on spectroscopy basic concepts using self-study.</p>
<p>In the absorption spectrum, if I shine light on a particular liquid of a single type of molecule it absorbs a specific frequency in the visible range. Now where I am struggling is once an electron absorbs a photon of a ... | https://chemistry.stackexchange.com/questions/187283/absorption-spectrum-and-re-emission-of-photon |
Question: <p>For example, potassium chloride released a purple colored flame?
Does it have to do with the energy level of the valence electrons in the metal cation that is being burned?</p>
Answer: <p>You are right, it depends on the energy level of valance electrons, but more precisely it depends on the difference b... | https://chemistry.stackexchange.com/questions/62450/why-do-different-metal-ions-release-different-colors-of-light |
Question: <p>I want to ask if the rotational-vibrational spectra of a molecule is related to any one mode of frequency or if it is related to the whole molecule?</p>
<p>Additionally, the vibrational levels that we say are composed of lower rotational energy levels. Are these vibrational energy levels of certain vibrat... | https://chemistry.stackexchange.com/questions/65016/rotational-vibrational-spectroscopy-of-a-molecule |
Question: <p>I (partially) understand how a breakdown voltage is applied, then the gas is ionized to cations and electrons. Then the electrons will accelerate to the cathode and knock off more electrons from other H2, creating a current ( which is the flow of electrons ). The electrons might excite the gas and the gas ... | https://chemistry.stackexchange.com/questions/69326/how-are-hydrogen-atoms-formed-in-hydrogen-discharge-tube |
Question: <p>I did an experiment where I analyzed the amount of caffeine and benzoate in soda via spectroscopy. I've got the absorbances and did all the math for everything, but I'm having a hard time figuring out why we had to add an acid to protonate the benzoate to form benzoic acid before running the spec.</p>
<p>... | https://chemistry.stackexchange.com/questions/71722/why-convert-benzoate-in-soda-to-benzoic-acid-for-spectroscopy-experiment |
Question: <p>Disclaimer: My background is computer science.</p>
<p>Is it possible to detect any gas using a visible light and near infrared (400 nm - 1000 nm) <a href="https://en.wikipedia.org/wiki/Hyperspectral_imaging" rel="nofollow noreferrer">hyper spectral imaging</a> camera? This can be related to gas leaks, pol... | https://chemistry.stackexchange.com/questions/71904/gas-spectra-in-the-400-nm-1000-nm-range |
Question: <p>I am trying to measure the absorbance of a solution at 882 nm, but this seems to be beyond the range of many UV-Vis spectrometers. Is this a job for the IR spectroscopy, or something else? I do not have much experience with IR spectroscopy.</p>
Answer: <p>No this is not a job for an IR machine. It all dep... | https://chemistry.stackexchange.com/questions/72541/how-to-measure-absorbance-at-882-nm |
Question: <p>What is the fastest or the most definite method (preferentially a single unexpensive method) for verifying the presence of a certain small orgnic molecule which is expected to be of >90% purity in a "powdry" sample (known solvent is also availble)? </p>
<p>Thank you in advance</p>
Answer: | https://chemistry.stackexchange.com/questions/73340/the-best-methods-to-identify-verify-the-presence-of-a-small-organic-molecule |
Question: <p>I have difficulty understanding the first sentence of the Introduction in the paper linked below. Can someone explain to me what is spectroscopic transition frequency and thermal bath? </p>
<blockquote>
<p>The question addressed here is how the modulation of the spectroscopic transition frequency Ω(t) ... | https://chemistry.stackexchange.com/questions/73481/spectroscopic-transition-frequency |
Question: <p>I am comparing two IR spectrums of the same molecule, one in the solid state and one in $\ce{CH2Cl2}$ solution. There is only one CO group in the molecule.</p>
<p>Why does the solid state spectrum show two carbonyl stretches, while the solution spectrum has only one carbonyl stretch?</p>
Answer: | https://chemistry.stackexchange.com/questions/74734/why-is-the-number-of-carbonyl-stretches-in-the-ir-spectrum-different-for-solid-s |
Question: <p>What is the differnce between a ground state electron and an excited state electron? Upon excitation what exactly changes about the electron?</p>
Answer: <p>You can think of electron states as book shelves and electron as a book. Is there anything different about that book if it stands on lower or upper s... | https://chemistry.stackexchange.com/questions/80481/what-is-the-difference-between-an-electron-in-ground-state-and-an-electron-in-ex |
Question: <p>In calculating the ratio of first state excited to unexcited chemical species using the Boltzmann distribution, are we assuming that we only have species in the unexcited and first state excited states? It seems to me that this must be the case, because there's no part of the equation that accounts for the... | https://chemistry.stackexchange.com/questions/104142/are-we-using-an-assumption-in-calculating-the-ratio-of-first-state-excited-to-un |
Question: <p>I know for a fact that a frequency domain spectrum can be obtained from a time domain spectrum using a Fourier transform - but can you do the reverse?</p>
<p>Also what are the advantages and disadvantages of the frequency and time domain spectra?</p>
Answer: <blockquote>
<p>Can you do the reverse?</p>... | https://chemistry.stackexchange.com/questions/104144/is-a-time-domain-spectrum-obtainable-from-a-frequency-domain-spectrum |
Question: <p>I have struggled to find a formal definition of cross-section of absorption; from what I've gathered, its best defined as 'the intensity of absorption'.</p>
<p>Wikipedia's formal definition of the molar extinction coefficient is 'how strongly a species absorbs EMR at a given wavelength, per molar concentr... | https://chemistry.stackexchange.com/questions/104464/are-the-molar-extinction-coefficient-and-cross-section-of-an-absorption-related |
Question: <p>Obviously the molar extinction coefficient is not equal to the probability of a photon of the associated wavelength being absorbed, but is it a measure of the probability i.e. the higher the value of the molar extinction coefficient, the higher the probability of absorption of the photon per molecule?</p>
... | https://chemistry.stackexchange.com/questions/104500/molar-extinction-coefficient-a-measure-of-the-probability-of-a-photon-of-the-ass |
Question: <p>The electrons in the 1s orbital of chlorine have a binding energy of 273 MJ/mol, but the 1s electrons in sulfur have a binding energy of 239 MJ/mol. Why is this?</p>
Answer: <p>Chlorine has 17 protons and Sulfur has 16. In the 1s orbital there is no ineer electron to provide shielding effect of repulsion.... | https://chemistry.stackexchange.com/questions/114386/binding-energy-question |
Question: <p>Usually what is the size (in nanometer) of the sample or target substance in IR and Raman Spectroscopy?</p>
<p>Which one has largest size of sample it can scan, how many molecules or atoms are involved? If you can make the size bigger or scan coverage bigger, then the more intense would be the IR or Raman... | https://chemistry.stackexchange.com/questions/122469/size-of-target-substance-in-ir-and-raman-spectroscopy |
Question: <p>Rayleigh scattering occurs when the dimensions of the scatter is much smaller than the wavelength of the incident electromagnetic radiation. </p>
<p>Mie scattering occurs when the dimensions of the scattered is much larger than the wavelength of the incident electromagnetic radiation. An example is when l... | https://chemistry.stackexchange.com/questions/123077/does-mie-scattering-occur-in-liquid-or-is-rayleigh-scattering |
Question: <p>The test for anions can be done with a platinum wire and a Bunsen flame.</p>
<p>My textbook says that it can also be done by preparing a solution of the given salt in water and ethanol and spraying it onto the Bunsen flame.</p>
<p>How do I prepare this solution in terms of how much water, ethanol and salt ... | https://chemistry.stackexchange.com/questions/150124/prepare-solution-of-salt-in-ethanol |
Question: <p>The chemical shift of enantiotopic protons is defined as follows in <a href="https://www.masterorganicchemistry.com/homotopic-enantiotopic-diastereotopic/" rel="nofollow noreferrer">Spectroscopy/Homotopic, Enantiotopic, Diastereotopic</a></p>
<blockquote>
<p>Enantiotopic protons have the same chemical shif... | https://chemistry.stackexchange.com/questions/151378/reason-for-different-chemical-shift-in-chiral-solvents-for-enantiotopic-protons |
Question: <p>IR is only absorbed my molecules with polar bonds
regardless of the overall polarity of the molecule , what about Microwaves ?</p>
Answer: <p>It depends on the strength of the incident EMF. Pure <span class="math-container">$\ce{H2}$</span> can be <a href="http://www.scholarpedia.org/article/Microwave_io... | https://chemistry.stackexchange.com/questions/105268/do-microwaves-heat-polar-molecules-or-molecules-with-polar-bonds |
Question: <p>I have two set of spectrum data, the first record (in wavenumbers) looks like this:</p>
<pre><code>...
967.0511723
968.9374611
970.8224407
972.7061127
974.5884787
976.4695403
...
</code></pre>
<p>And the second record (again, wavenumbers) umber looks like this:</p>
<pre><code>...
955.9630179
957.8733753
95... | https://chemistry.stackexchange.com/questions/162220/how-to-combine-raman-spectrum-data-with-different-wavenumber |
Question: <p>Since my last post yesterday, I found some leads and started to analyse my data. But then I started encountering more doubts, questions and confusion. Any help will be highly appreciated and will help me in speeding my research.</p>
<p>For analysis, I am matching the peak binding energy for each orbital fo... | https://chemistry.stackexchange.com/questions/163959/how-to-guess-the-chemical-state-in-which-particular-element-will-be-present-from |
Question: <p>Does anyone know what is scattering coefficient, absorption coefficient and extinction coefficient, and how to separate them experimentally?</p>
Answer: <p>In most applications, these terms are used interchangeably.</p>
<p>Most absorbance spectrophotometers work by measuring the intensity of the light be... | https://chemistry.stackexchange.com/questions/33223/several-coefficient-differences-in-uv-vis-spectroscopy |
Question: <p>When doing regression or classification when faced with a categorical attribute with <span class="math-container">$n$</span> possible values there are two options:</p>
<ol>
<li>Feed this attribute directly into your model.</li>
<li>Partition your data into <span class="math-container">$n$</span> pieces bas... | https://datascience.stackexchange.com/questions/76222/when-is-it-appropriate-to-split-a-dataset-on-a-categorical-value-and-generate-n |
Question: <p>Assume I want to predict if I'm fit in the morning. One feature is the last time I was online. Now this feature is tricky: If I take the hour, then a classifier might have a difficult time with it because 23 is numerically closer to 20 than to 0, but actually the time 23 o'clock is closer to 0 o'clock.</p>... | https://datascience.stackexchange.com/questions/23933/how-can-i-deal-with-circular-features-like-hours |
Question: <p>Problem is stated: we have giant csv file with one target column and rest are inputs, we don't know these features impact target but we would like to use algorithm that besides using linear and non-linear transformations will also take into account that right solution would be some_feature_A/some_feature_B... | https://datascience.stackexchange.com/questions/55507/problem-of-finding-best-combination-of-features-when-desired-feature-is-feature |
Question: <p>I have been struggling to find proof for that but I couldnt</p>
<p>Every time I prepare dataset I face the same issue</p>
<p>when a column is a classification such as <code>CountryCode</code> or <code>TaskType</code> in this dataset</p>
<pre><code>TaskType CountryCode Target
1 61 Red... | https://datascience.stackexchange.com/questions/57465/to-one-hot-encode-or-not-to-one-hot-encode |
Question: <p>Let's say I have a data set like the following:</p>
<p><code>file group_a_co_1 group_a_co_2 group_b_co_1 group_b_co_2
file_1 0.8 0.2 0.3 0.7
file_2 0.1 0.9 0.2 0.8
file_3 0.5 0.5 0.7 0.3
...
</code></p>
<p>I wonder, whether there are ways/tricks to tell the model about the group information... | https://datascience.stackexchange.com/questions/64693/how-to-use-feature-group |
Question: <p>Does anyone know any good search algorithms for feature optimization that search through every possible combination to find the optimal combination of features for maximum predictive power? (Permutations are not important).</p>
<p>So far I have been using Recursive Feature Elimination (RFE), which trains a... | https://datascience.stackexchange.com/questions/104412/are-there-any-search-algorithms-for-feature-optimization-similar-to-rfe-but-whi |
Question: <p>This is rather a practical question. I'm looking for an efficient way of calculating the frequency of an event for a large number of samples. Here's a more concrete example.</p>
<p>Let's say that I have a system with millions of users. Each user has so many different features that I can use to categorize t... | https://datascience.stackexchange.com/questions/111996/an-efficient-way-of-calculating-estimating-frequency-spectrum-for-an-event |
Question: <p>I am trying to understand how I can encode categorical variables using likelihood estimation, but have had little success so far.</p>
<p>Any suggestions would be greatly appreciated.</p>
Answer: <p>I was learning this topic too, and these are what I found:</p>
<ul>
<li><p>This type of encoding is called... | https://datascience.stackexchange.com/questions/11024/encoding-categorical-variables-using-likelihood-estimation |
Question: <p><strong>BACKGROUND:</strong> I have dataset that includes <code>Race</code> (e.g., White, Black) and <code>Ethnicity</code> (e.g., Hispanic, Non-Hispanic) as <strong>observed variables</strong>. The dataset also includes <code>Race_Ethnicity</code> (e.g., Hispanic White, Non-Hispanic Black) as an <strong... | https://datascience.stackexchange.com/questions/116904/should-original-features-be-retained-in-the-model-after-using-them-to-engineer-n |
Question: <p>There is one behavior of <a href="http://scikit-learn.org/stable/modules/generated/sklearn.preprocessing.LabelBinarizer.html" rel="nofollow noreferrer">labelbinarizer</a> </p>
<pre><code>import numpy as np
from sklearn import preprocessing
lb = preprocessing.LabelBinarizer()
lb.fit(np.array([[0, 1, 1], [1... | https://datascience.stackexchange.com/questions/27130/2d-matrix-for-labelbinarizer |
Question: <p>I have a feature for machine learning (using methods like SVM, naive bayes, neural network and random forest) called member duration as follows:
Should I make it as numerical or categorical data?</p>
<p><a href="https://i.sstatic.net/fyMsI.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/fyM... | https://datascience.stackexchange.com/questions/17124/numerical-or-categorical-data |
Question: <p>I have a feature for machine learning as follow that skew to the left, and only have number in certain number range (here 0-2000). Will skewness and range of number affect the learning? If yes what should I do?</p>
<p><a href="https://i.sstatic.net/M00zz.png" rel="nofollow noreferrer"><img src="https://i.... | https://datascience.stackexchange.com/questions/17125/effect-of-skewness-and-data-range-in-machine-learning |
Question: <p>Let's say I wan't to predict the lifespan of an ad in a listing.</p>
<p>I know a bunch of thing from the ad like:</p>
<ul>
<li>the title</li>
<li>the price</li>
<li>the location</li>
<li>etc</li>
</ul>
<p>The target value is the duration of the ad in the listing before it's being removed (item has been ... | https://datascience.stackexchange.com/questions/35730/what-is-a-good-approach-for-a-lifespan |
Question: <p>If I have generated features using state of the art feature engineering methods of a dataset, can I use it for any kind of algorithm to build the model apart from few modifications in the features so as to plug in different algorithm?</p>
<p>Is there any dependency of algorithm while building features fro... | https://datascience.stackexchange.com/questions/32491/is-it-safe-to-say-if-features-are-generated-once-for-a-dataset-it-may-be-used-f |
Question: <p>Given hourly updates of precipitation amount (for the preceding hour) and temperature, how would you calculate if it's slippery or not?</p>
Answer: <p>A purely physical model, i.e. no training data, I would say something along the lines of: IF temperature was (and still is) below 0 centigrade and precipit... | https://datascience.stackexchange.com/questions/131176/calculating-risk-or-amount-of-slipperiness-based-on-historical-weather-data |
Question: <p>While feature engineering and deriving features why should I not use I’d as a field for tasks like regressions</p>
Answer: <p>An Id, like a person’s name, is typically a unique identifier with no meaningful relationship to the target variable. Since it doesn’t carry any inherent pattern or information rel... | https://datascience.stackexchange.com/questions/130496/why-should-i-not-use-id-as-a-field-in-feature-engineering-for-ml |
Question: <p>I have a feature which has specific categorical values ex(Technology, Hardware, Software, Marketing, Evnts etc). Based on this and some other features, I am trying to classify the dataset into 2 categories IsSoftwareSystem or NotSoftwareSystem. In this case is this cause a reduce in accuracy because i am f... | https://datascience.stackexchange.com/questions/90469/cyclic-dependency-between-feature-and-predictor-class |
Question: <p>In the classical linear regression implementation, if I suspect the square of the values of the column is correlated to the target, then I actually need to create a new column with the squares for the algorithm to make use of that.</p>
<p>Is this also necessary when using neural networks? I know it's a bro... | https://datascience.stackexchange.com/questions/80938/do-i-need-to-square-a-column-if-i-want-a-neural-network-to-try-using-that |
Question: <p>I'm working on one use case where I have to explore source code repo files. Different files will be a categorical values for me. But with such large number of files, One Hot Encoding comes out to be very large.</p>
<p>Also, all files are divided among unique modules, such that each files belongs to a speci... | https://datascience.stackexchange.com/questions/82757/reduce-categorical-values |
Question: <p>I have database with three columns, y,x1 and x2:</p>
<pre><code>>>>y x1 x2
0 0.25 -19.3 -25.1
1 0.24 -18.2 -26.7
2 0.81 -45.2 -31.4
...
</code></pre>
<p>I want to create more features based on the x columns.
until now I have just created random functions and tries to chec... | https://datascience.stackexchange.com/questions/85551/generate-new-features-from-two-columns |
Question: <p>Say for example I am building a model to predict a customer churn event from Spotify, with my target being whether a customer churns in the next 90 days.</p>
<p>One feature I might expect could be predictive of this event is customers checking their billing statements online - so I might engineer features ... | https://datascience.stackexchange.com/questions/84633/what-is-best-practice-to-feature-engineer-from-prior-event-counts |
Question: <p>I need some advice for my feature engineering.
Suppose I have 90 days follow-up data. on 12 patients and I have the vital status of the patients at the end of these 90 days (deceased=1, alive=0)</p>
<pre><code>ID<-as.factor(c(1,1,1,2,2,2,2,3,3,4,4,4))
time<-c(0,12,36,0,7,23,68,0,23,0,32,45)
Age<-r... | https://datascience.stackexchange.com/questions/88029/feature-engineering-and-longitudinal-data |
Question: <p>Say you have a binomial distribution with $p$ very small ($\approx 0.001$). </p>
<p>You are asked to predict the conditional success rate $SR=S/T$ with $S$ successes out of $T$ trials given a set of conditions $X$.</p>
<p>One would expect (correct me if I'm wrong, though I ran simulations and am quite co... | https://datascience.stackexchange.com/questions/10463/skewed-binomial-data-for-small-p |
Question: <p>I have a few Independent variables that's normal and a Dependent variables that's skewed , I pick <strong>log(feature+SHIFT)</strong> to correct skewness. The procedure I follow to get prediction is just take <strong>exp(predictions)-SHIFT</strong>.</p>
<p>Now how do I get my predictions for the following... | https://datascience.stackexchange.com/questions/17542/transformation-of-dependent-and-independent-variables |
Question: <p>I've been using GIST, HOG and SURF descriptors for extracting features from different collections of Chest-X-rays and measuring performance using accuracy and area under the curve. These collections are obtained using different machinery, from different medical institutions, and, with different pixel resol... | https://datascience.stackexchange.com/questions/24764/why-is-there-a-difference-in-performance-across-the-feature-descriptors-for-the |
Question: <p>I am working on the KDD dataset given in this <a href="https://www.kaggle.com/c/kddcup2012-track1#Description" rel="nofollow noreferrer">link</a>. </p>
<p>The dataset is related to a typical recommendation systems dataset. So you find an item and information about the item. One of the information given ab... | https://datascience.stackexchange.com/questions/25910/feature-engineering-for-hierarchical-data |
Question: <p>Are there any differences between <a href="https://pandas.pydata.org/pandas-docs/stable/generated/pandas.get_dummies.html" rel="nofollow noreferrer">get_dummies</a> and <a href="http://scikit-learn.org/stable/modules/generated/sklearn.preprocessing.LabelBinarizer.html" rel="nofollow noreferrer">labelbinari... | https://datascience.stackexchange.com/questions/27126/differences-of-get-dummies-and-labelbinarizer |
Question: <p>Days ago,One AI financial service provider offered us a lesson and mentioned that you are supposed to perform specific feature engineering according to the specific algorithm you are using.For example,when using logistics regression,fitting more features（uncorrelated）like binning the continuous variable in... | https://datascience.stackexchange.com/questions/28398/specific-feature-engineering-for-specific-algorithm |
Question: <p>I'm pretty new to machine learning.</p>
<p>I know I can represent a set of discrete values as a vector of 0/1 values. For instance, in the set of features {a, b, c, d, e}, the subset containing <code>{a, c}</code> can be represented as <code>[1, 0, 1, 0, 0]</code> and the subset containing <code>{c, d, e}... | https://datascience.stackexchange.com/questions/29693/how-to-represent-a-set-of-sets-as-a-vector |
Question: <p>I have some data in raw csv files which I would like to store in a MySQL database. The problem is there are constant feature engineering done on this dataset so coming up with one schema to fit all the needs is not possible. The approach I thought of was to have one main table where the original data is ... | https://datascience.stackexchange.com/questions/32414/storing-engineered-features-in-a-database |
Question: <p>I am working on a problem in which I have several instances that have predictors that have activity over various different time periods (i.e. <3 months to well over 20 months.) Originally I attempted to use knowledge I have about this problem (it is an opportunity to sale conversion model) and learned t... | https://datascience.stackexchange.com/questions/34423/how-to-aggregate-data-where-instances-occur-over-different-time-intervals |
Question: <p>i have created some new features for my model. I found people use kde plot to find out the correlation between the created feature and the target variable, but I am not really sure how to find the correlation from kde.</p>
<p>Any help on how to interpret the correlation from kde plot will very helpful </p... | https://datascience.stackexchange.com/questions/36575/kde-plot-for-interpreting-the-correlation |
Question: <p>I'm using decision tree learning to try and classify a device based its components. Different devices have a different number of components and the location of these components within the device is important.</p>
<p>Device 1 might have components 9, 3, 8, 4, and 1 in that order.
Then device 2 might have c... | https://datascience.stackexchange.com/questions/42494/how-important-is-it-for-each-row-of-data-to-have-the-same-number-of-features |
Question: <p>I have a multi class classification problem where I should predict the passengers for flights (0-7 classes). The training set consists of the following features:</p>
<ul>
<li>Date of the flight</li>
<li>Mean of the weeks that the passengers bought their tickets</li>
<li>Standard Deviation of the above</li... | https://datascience.stackexchange.com/questions/43514/feature-engineering-from-date-mean-and-standard-deviation |
Question: <p>I am facing a dilemma with a project of mine. One of the variables (numerical) doesn't have enough data i,e almost 99% data are missing. However, upon talking to the domain experts, it appears that the particular variable is important to the problem we are trying to solve (model). Initially, I thought of c... | https://datascience.stackexchange.com/questions/45284/problem-with-important-feature-having-a-lot-of-missing-value |
Question: <p>I have a dataset, where a particular feature is a collection of many JSON objects for a single feature.</p>
<pre><code>Timestamp Observations
1 {"name":"bob", "place":"TX"},{"name":"ann", "place":"NY"},{"name":"jack", "place":"MA"},{"name":"jill", "place":"CA"}
2 {"name":"bob", "p... | https://datascience.stackexchange.com/questions/45996/feature-encoding-for-multiple-json-objects |
Question: <p>I want to create a new metric based on some features but dont know how to start. I basically want to create a "job satisfaction level" metric based on some features. The features could be work hours, shift, If working on weekend and so on. I dont know how to start. In ideal world, I want to comp up with we... | https://datascience.stackexchange.com/questions/48361/creating-a-metric-based-on-some-features |
Question: <blockquote>
<p>Goal: Predict a performance score of a place of interest in a given city based on (amongst others), the number of restaurants within 200m. <span class="math-container">$\\$</span></p>
<p>Dataset: <span class="math-container">$D$</span> with a feature <span class="math-container">$x$</sp... | https://datascience.stackexchange.com/questions/53692/transformation-of-non-categorical-discrete-feature |
Question: <p>I have a data set of 700+ mil records with a feature that should yield good predictive power. The problem is that it has far more unique values than it should. The 10k+ unique values should map to about 150. I have that list of 150 values I want them to map to. Thinking about using a distance algorithm (le... | https://datascience.stackexchange.com/questions/56112/reduction-of-feature-values |
Question: <p>Could changing the hyperparameters of a model change <strong><em>relative</em></strong> feature importance?</p>
Answer: <p>Yes. The most obvious example is when using a Lasso regression : for an increasing <span class="math-container">$\alpha$</span> parameter you will have more and more coefficients set ... | https://datascience.stackexchange.com/questions/71818/relative-feature-importance-w-r-t-hyperparameters |
Question: <p>Hi all I would love to hear your answers on this. Lets say I have two variables, voltage and current, in my data set. I could add another feature by squaring current (so as to calculate power). </p>
<p>Is this an example of feature engineering?</p>
<p>Recently I tried to predict on a diameter prediction ... | https://datascience.stackexchange.com/questions/72584/is-it-suitable-to-change-a-feature-by-itself-to-generate-an-another-feature |
Question: <p>In the tutorial, they normalize the data and say "The mean and standard deviation should only be computed using the training data"</p>
<p>What does this refer to? Why should you only use the training data?</p>
Answer: <p>When building <strong>any</strong> Machine Learning model, the only observable data ... | https://datascience.stackexchange.com/questions/74018/tensor-flow-time-series-tutorial-question |
Question: <p>I've been exploring the use of XGBoost in many different applications. Up to now, I always find the best results with shallow trees (from 1 to 3 levels), with the rest of the parameters very dependent on the problem.</p>
<p>On my current assignment, I found that I get a much better performance if I use >... | https://datascience.stackexchange.com/questions/89661/xgboost-with-deep-trees |
Question: <p>I have a scenario in which I'm required to run my analysis at the Account level. One of the features that I'd like to look at is the no. of subscriptions against an account. There can be multiple subscriptions against one account. I wonder how I can "aggregate" these multiple subscriptions and roll them up... | https://datascience.stackexchange.com/questions/60589/aggregate-categorical-data |
Question: <p>I have time-series data that track event occurrence in 3 locations. Here's a sample:</p>
<pre><code> Count Total
Location A B C
Date
2018-06-22 0 1 1 2
2018-06-23 2 1 0 3
2018-06-24 0 0 1 1
2018-06-25 2 2 1 ... | https://datascience.stackexchange.com/questions/77921/test-for-feature-dependencies-in-time-series-modelling |
Question: <p>Imagine, there is a service, providing credit history for customers in form of list of his loans. Let's call it <strong>my-loan-service</strong>. For the sake of simplicity - I can <code>GET http://my-loan-service/42</code> (where 42 is my customer id) and get back <code>json</code></p>
<pre class="lang-js... | https://datascience.stackexchange.com/questions/90453/serving-feature-pipeline |
Question: <p>When Machine Learning libraries don't support categorical features those features can be one-hot encoded into a series of binary feature columns. I have a feature that represents a sequence or permutation of values and I want to transform it into something scikit-learn or similar ML libraries can use. Wh... | https://datascience.stackexchange.com/questions/90700/how-can-i-transform-a-sequence-into-features |
Question: <p>I am aiming to predict the number of days it takes to sell a given property, let's call this variable "DaysForSale" - in short DfS</p>
<p>Using the DfS I created a variable called "median_dfs_grouped_street_name" which returns the median days it takes to sell a property for the differen... | https://datascience.stackexchange.com/questions/80770/i-do-feature-engineering-on-the-full-dataset-is-this-wrong |
Question: <p><a href="https://www.reddit.com/r/MachineLearning/comments/ma59mt/d_is_my_idea_of_a_feature_store_wrong/" rel="nofollow noreferrer">Cross-posted on Reddit ML</a>.</p>
<p>Should a Feature Store be part of an enterprise data catalog?</p>
<p>To me, a feature store seems to be a highly niche data catalog but m... | https://datascience.stackexchange.com/questions/90980/is-my-idea-of-a-feature-store-wrong |
Question: <p>I have 6 input features <span class="math-container">$[m1,m2,m3,m4,m5,m6]$</span>.</p>
<p>I am trying to build a model that can predict the value of all 6 of these values using <span class="math-container">$[m1,m2,m3]$</span>. However, I have the option of asking for another feature from <span class="math-... | https://datascience.stackexchange.com/questions/96774/using-on-demand-features-in-machine-learning |
Question: <p>When fitting a model with the AutoTS package, it will fit a number of models per generation (it uses the genetic algorithm). However, there does not seem to be an option to edit the number of different models that are evaluation per generation.</p>
<p>As such, I am wondering how to edit the number of diffe... | https://datascience.stackexchange.com/questions/131259/changing-the-number-of-model-evaluations-per-generation |
Question: <p>I have built an XGBoost classification model in Python on an imbalanced dataset (~1 million positive values and ~12 million negative values), where the features are binary user interaction with web page elements (e.g. did the user scroll to reviews or not) and the target is a binary retail action. My ultim... | https://datascience.stackexchange.com/questions/65608/xgboost-feature-importance-permutation-importance-and-model-evaluation-criteri |
Question: <p>I don't understand why using the <em>test set</em> for model <strong>evaluation</strong> is a bad idea.</p>
<p>I completely understand why you should not use your test set to <strong>train</strong> your model (because in that case, you would be memorizing and you just cannot tell whether your model will g... | https://datascience.stackexchange.com/questions/23309/why-exactly-using-a-test-set-for-model-evaluation-is-a-bad-idea |
Question: <p>I'm working on topic modeling and I have generated clusters with two different methods.</p>
<p>How can I evaluate which method performs better than the other?</p>
<p><a href="https://i.sstatic.net/2JGKo.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/2JGKo.png" alt="" /></a><a href="https://... | https://datascience.stackexchange.com/questions/126302/topic-modeling-evaluation |
Question: <p><strong>My method of evaluating a model is the following :</strong> </p>
<ol>
<li>Split the training data set and do cross validation to obtain an accuracy of my model on my cross validation data set.</li>
<li>Use the parameters that gave me the best accuracy and use predict() on my test data set ( hold-o... | https://datascience.stackexchange.com/questions/52004/error-analysis-and-evaluation-of-a-model-using-python |
Question: <p>I was reading <a href="https://changhsinlee.com/better-validation-test/" rel="nofollow noreferrer">a blog post</a> about improving machine-learning model train/validate/test splits. Towards the end was this remark:</p>
<blockquote>
<p>I say we should be more creative in the way we test machine learning mod... | https://datascience.stackexchange.com/questions/116626/can-using-model-evaluation-metrics-to-choose-a-model-cause-data-leakage |
Question: <p>Suppose that we have train a model (as defined by its hyperparameters) and we evaluated it on a test set using some performance metric (say <span class="math-container">$R^2$</span>). If we now train the same model (as defined by its hyperparameters) on a different training data we will get (probably) a di... | https://datascience.stackexchange.com/questions/110026/bias-variance-trade-off-and-model-evaluation |
Question: <p>A colleague and I are working on a churn model and reached an impasse:</p>
<p>Our data set is for a global product. We've been asked to look at the US market only.</p>
<p>When we subset the data to the US only, the classifier evaluation metrics are lower than when we use the total global data set.</p>
<p>M... | https://datascience.stackexchange.com/questions/113772/more-representative-data-set-or-higher-model-evaluation-metrics |
Question: <p>In supervised machine learning, are there any evaluation approaches <em>beside</em> using a fixed holdout test dataset, which allow me as a scientist to <strong>manually</strong> compare preprocessing approaches, without leaking information from the test dataset.</p>
<p>For example, if I want to compare fe... | https://datascience.stackexchange.com/questions/128804/model-evaluation-approach-allowing-manual-experimentation-without-data-leakage |
Question: <p>I am a newbie here and trying to make sense out of the scores from <code>model.evaluate</code> from what I am actually seeing in <code>model.predict</code></p>
<p>I have a created a CNN model for the Google Audio Set data and achieved a 99%+ accuracy on training.</p>
<p>Here is how I do the prediction</p... | https://datascience.stackexchange.com/questions/64844/keras-model-evaluation-accuracy-vs-observation |
Question: <p>After study in time series analysis, I recognized RMSE and MAPE are the best evaluation metrics for used model in real time series application. But my queries are below as this is my first practice application project in time series analysis:</p>
<p>If I use past 1 year data for training and forecast for ... | https://datascience.stackexchange.com/questions/82758/time-series-analysis-model-evaluation-performance-metrics-integration-in-time-se |
Question: <p>I would like to get help with evaluation of my classification model. It is a typical model that for each input produces vector of floats that represents probabilities of labels and I classify the input with label with highest probability.</p>
<p>But I have a problem with evaluation of this model. The reaso... | https://datascience.stackexchange.com/questions/131495/evaluation-of-model-on-imperfect-validation-set |
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