question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>I recently read a paper in which the authors claim that in order to compare the forecasting performance of two non-nested models, models A and B, a valid procedure is to fit models A and B on the same data set, and compare the average likelihood of the fitted models computed on the hold-out data set. All that is req... | 74,016 |
<p>Which 2-tailed test is best to use to compare means/medians when one variable has a normal distribution and the other does not?</p> | 39,451 |
<p>Is there a difference between ANCOVA (as performed under the 'General Linear Model (GLM)') and Hierarchical Regression (as performed under 'Regression') in SPSS?</p>
<p>I am testing the main effects and interaction of X1 (continuous) and X2 (categorical) on Y (continuous).</p>
<p>I understand GLM incorporates regr... | 74,017 |
<p>Can anyone tell me what exactly a cross-validation analysis gives as result?
Is it just the average accuracy or does it give any model with parameters tuned? </p>
<p>Because, I heard somewhere that cross-validation is used for parameter tuning.</p> | 36,638 |
<p>I am studying a population of individuals who all begin with a measureable score of interest (ranging from -2 to 2) [call it "old"], then they all undergo a change to a new score (also ranging from -2 to 2) ["new"]. Thus all the variation is in the change (which can be positive or negative), and there are also a var... | 74,018 |
<p>I ran a within subjects repeated measures experiment, where the independent variable had 3 levels. The dependent variable is a measure of correctness and is recorded as either correct / incorrect. Time taken to provide an answer was also recorded.</p>
<p>A within subjects repeated measures ANOVA is used to establis... | 38,142 |
<p>Based on the responses from the question <a href="http://stats.stackexchange.com/questions/28086/how-to-draw-a-side-by-side-plot-mentioned-in-graphical-display-as-an-aid-to-ana">How to draw a side-by-side plot mentioned in "Graphical Display as an Aid to Analysis"</a>, I am considering implementing the fun... | 41,740 |
<p>Standard deck has 52 cards, 26 Red and 26 Black. A run is a maximum contiguous block of cards, which has the same color.</p>
<p>Eg.</p>
<ul>
<li>(R,B,R,B,...,R,B) has 52 runs.</li>
<li>(R,R,R,...,R,B,B,B,...,B) has 2 runs.</li>
</ul>
<p>What is the expected number of runs in a shuffled deck of cards?</p> | 74,019 |
<p>Following to the recent questions we had <a href="http://stats.stackexchange.com/questions/1818/how-to-determine-the-sample-size-needed-for-repeated-measurement-anova/1823#1823">here</a>.</p>
<p>I was hopping to know if anyone had come across or can share <strong>R code for performing a custom power analysis based ... | 74,020 |
<p>What is the distribution of the following monomial?
$$X^a \cdot Y^b$$
where $X$ and $Y$ are normal random variables and $a$ and $b$ are natural numbers.</p>
<p>For example, when $X \sim N(0,1)$, $a=2$, and $b=0$ it is a Chi-squared distribution, which has a variance of 2.</p>
<p>What if we have $n$ independent var... | 74,021 |
<p>When studying time series, I once heard the statement that</p>
<blockquote>
<p>unit root test is less powerful.</p>
</blockquote>
<p>I hereby have two questions:</p>
<ol>
<li>What does it mean for a test to be powerful?</li>
<li>What causes the unit root test to be less powerful?</li>
</ol> | 36,642 |
<p>My lecturer just covered the <strong>Lindberg-Levy central limit theorem</strong> and the multivariate version, the <strong>Lindberg-fuller CLT</strong>. I understood the basic concept and I can derive it, etc. But it would help my understanding a lot if someone could explain how all this used in real life applicati... | 74,022 |
<p>I tried to find some relation between these distance (loss) measures, but couldn't find any references. However, I think it must something like this:
$$
\sqrt 2*D_{KL} < L_1 < L_2
$$
Is that right?</p> | 36,644 |
<p>Which correlation coefficient is the most appropriate to compare 2 time series? I want to compare the variation of one variable for 2 regions, have regional data for the last 30 years. Is Pearson correlation ok or should I rely on Kendall's tau b or Spearman's rho and why? I tried to google it and analyse what I fou... | 74,023 |
<p>I have learnt the definition of AIC for parametric model. But, what I want to know is that is there a semi-parametric version of AIC?
Have you heard about it? And if you know, please show me a link, so I can have a look. </p> | 41,742 |
<p>Here is the problem: I am making a machine learning algorithm that takes the inputs and outputs of some software I've written, and I don't know how many datalines to produce to get results that are a 'good' fit. I realize the answer is 'the more the better' but I'm looking for any sort of minimum requirement. I also... | 74,024 |
<p>I have implemented a three-way anova with type III sum of squares in c++. Since some of my experiments (observations) are more important (more informative), I want to give them a higher weight in my analysis. For example, an experiment which is very important has a weight of 10, and a relatively important one has a ... | 74,025 |
<p>I iterated my 10-fold cross validation 100 times for several methods. Now I want to use a t-test to test if the results are significant. However, I'm not sure what the sample size is.
Is the sample size the original amount of samples, or is it the original amount of samples x 100?</p>
<h2>edit:</h2>
<p>For univer... | 46,718 |
<p>I have a collection of $n$ datapoints $(y_i,\bf{x}_i)$ in $\mathbb{R}^{p+1}$ and would like to estimate the following model in <code>R</code>:</p>
<p>$$\underset{\bf{b}\in\mathbb{R}^{p}}{\arg.\min}\;\sum_{i=1}^n(y_i-\bf{x}_i'\bf{b})^2$$ </p>
<p>$$u.c.\;\;\;0\leq \bf{x}_i'\bf{b}\leq 1\;\;\;\forall i$$</p>
<p>anybo... | 74,026 |
<p>Let's assume we have predictors x1-x5 and dependent variables y1-y9 in one dataset.
We have a certain hypothesis about x1: it should have differently strong effects on our 9 dependent variables y1-y9. </p>
<p>We perform 9 regressions, and find that x1 significantly predicts all y with p<.001.
Now we want to fin... | 36,649 |
<p>I'm trying to program impulse response functions for a VAR model using Cholesky decomposition. The thing is I do not completely understand how I should do this when I read in the literature. Suppose I have:</p>
<p>$$
\begin{bmatrix}x_t\\y_t\\z_t\end{bmatrix}=\begin{bmatrix}\alpha_1\\\alpha_2\\\alpha_3\end{bmatrix}+... | 36,651 |
<p>I estimated a Partial Least Squares model where the X matrix had normalized columns. Now I want to predict the value for a new instance (which is a frequency vector summing to one.) I assume that if I just use the raw frequency values, the predicted value won't be on the same scale as the scenario where my 'new' ins... | 50 |
<p>My work involves building statistical / econometric models using R, SPSS modeler. I am also doing my PhD (part time) in econometrics. In order to do more advanced data / model visualisation I am thinking about to pick up another programming language. Any suggestion will be much appreciated. </p> | 74,027 |
<p>A treatment was given to one hand of a subject, and a single outcome metric is measured for both hands, twice pre and several times post treatment. </p>
<p>What is best practice for assessing effectiveness of treatment? </p>
<p>Treated and Untreated "groups" really are paired.</p> | 74,028 |
<p>I have to design an experiment where tool wear is a factor (not a response). I'm not trying to study tool wear minimizing. I'm trying to study the effect of tool wear along with 3 other factors on the number of a certain defect type.</p>
<p>What kind of design should I use? I considered dividing the tool wear into ... | 36,653 |
<p>What is a good loss function for a predictive model used by gamblers?</p>
<p>I've been reading a bit about loss functions recently. I've always just went with MSE (e.g., for a couple of neural network projects) and didn't ask questions. I didn't realize exactly how arbitrary MSE actually is. And speaking of this, c... | 36,654 |
<p>I have hourly utility bills for two years. The first year's data are from before a retrofit was performed on a home and the second year is after the retrofit was performed. </p>
<p>How do I compare the two time series statistically to make claims of demand savings during a specific time period of the day. Can this ... | 48,321 |
<p>My first and I think naive question here.</p>
<p>I am trying to model a certain business, and the simplest model I am willing to test is:
1. there is a bag of differently biased coins.
2. every step, a single coin is chosen with equal probability.
3. the chosen coin is flipped and returned to the bag.</p>
<p>The b... | 74,029 |
<p>I want to study relations between sites categories and species
abundances through PCoA or CAP using vegan::capscale. For doing so, I
overlay species scores on my ordination. However, I am getting confused
with the different scaling options and their interpretation. From what I
understood:
With scaling=1, arrow s... | 74,030 |
<p>This is probably going to sound extremely stupid, but it's part of a larger question, about sample distribution of means, that I'm having problems understanding, so please bear with me.</p>
<p>If I record the time between planes landing, and have 250 observations, are those 250 observations my "population", or does... | 74,031 |
<p>I don't know a lot about sampling methods. </p>
<p>I have a large population of size 2,000,000. I used one of those sample size calculators. It says that I need sample size of approximately 10,000.</p>
<p>I am trying to find the probability <strong>p</strong> of success for the population. It is not feasible f... | 74,032 |
<p>I am trying to estimate the price elasticity of supply for small scale farmers in Malawi and I have time series data for 34 years. I have two problems: First, the prices are very low such that when I take their logs am getting negative values, as a remedy i added 1 to each value and i got positive logs but i don't k... | 74,033 |
<p>In the English Championship division, there are 24 teams, 8 of which have names starting with the letter B (e.g.Bolton) Tonight, (5th March 2013) all 24 teams in this division are playing each other. By a coincidence, the 8 teams starting with B are playing each other, i.e. 4 of the games involve these 8 teams (ther... | 74,034 |
<p>I performed principal components analysis on continuous variables describing 16 languages. Using the first two axes, which explain 76% of variance, I need to calculate the distance between each pair of languages as appeared on the first two axes; to test in a Mantel test the correlation between distances in linguist... | 74,035 |
<p>I have time series data for a set of cities that goes back for about 10 years. I also have the data at the state level for almost 30 years. There was an event that occurred about 20 years ago, that is captured in the longer, state level data, but not the city data, that I would like to investigate at the city level.... | 36,659 |
<p>What is the best out-of-the-box 2-class classifier? Yes, I guess that's the million dollar question, and yes, I'm aware of the <a href="http://www.no-free-lunch.org/">no free lunch theorem</a>, and I've also read the previous questions:</p>
<ul>
<li><a href="http://stats.stackexchange.com/questions/258/poll-what-i... | 48,332 |
<p>When estimating the confidence interval of mean, I think both the bootstrap t method and the nonparametric bootstrap method can apply, but the former requires a little more computation. </p>
<p>I wonder what the advantages and disadvantages of bootstrap t over the normal nonparametric bootstrap are? Why? </p>
<p>A... | 74,036 |
<p>I have a total population of 31, of these I have a treatment finishing population of 20.</p>
<p>I want to run a test on SPSS to identify if there are any significant differences between the 20 individuals that completed the treatment and the group as a whole.</p>
<p>The variables I am trying to compare are age, we... | 74,037 |
<p>(Possibly related to <a href="http://stats.stackexchange.com/questions/17342/is-there-a-nonparametric-equivalent-of-tukey-hsd">Is there a nonparametric equivalent of Tukey HSD?</a>)</p>
<p>Given a set of several exponentially distributed variables (representing data which is modeled this way), I'd like to check whe... | 74,038 |
<p>In the following problem, check that it is appropriate to use the normal approximation to the binomial. Then use the normal distribution to estimate the requested probabilities.</p>
<p>It is known that 85% of all new products introduced in grocery stores fail (are taken off the market) within 2 years. If a grocery ... | 36,663 |
<p>I am trying to grasp what exactly is "estimated" in the E-step of the algorithm. </p>
<p>According to all definitions, in E-step the "conditional expectation values , or posterior probabilities of the hidden variables" are computed, using the Bayes formula ( posterior probability=prior( or marginal prob.) x likelih... | 36,664 |
<p>I like to set up a 2 way repeated measures anova. I compare 4 models with 4 ages and see if the results differ, this should result in around 16 groups, since 4*4=16 (so far so good)</p>
<p>However from some groups I don't have the data so I still have 2 factors to test for but not longer 16 groups but 15-14.</p>
<... | 36,665 |
<p>I have a textual classification problem that consists of two categories- zero an one.
Up until now I tried solving it by creating a Document Term Matrix, and to run it through SVM (using RTextTools package).
Here's a code snippet: (R)</p>
<pre><code>models <- train_models(container, algorithms=c("SVM"))
results ... | 74,039 |
<p>If I would like to fit random intercept and slope and if I write it as (color|writer) compared to (1+color|writer), are they the same?</p> | 74,040 |
<p>For example, the lists can be something like:
$$\{1.123213, 5.154543, 2.134121, 7.34534, 12.223432, 8.16571, 100.45645, 222.423\}$$
I want to remove $\{100.45645, 222.423\}$.</p>
<p>$$\{232.123213, 323.154543, 232.134121, 123.34534, 222.223432, 8545.16571,\\ 4335.45645, 1222.423\}$$
I want to remove $\{8545.16571,... | 36,666 |
<p>Let's say that I have a picture like the one in figure. This look like an histogram, but actually is not, in the sense that I did not produce the figure starting from a dataset of values. In fact, I only have the probability (the y axis) for each bar. I also have the center point of each bin, and the bin width of ea... | 74,041 |
<p>Im newbie in Image Processing field, and I got many term that wierd. There are :</p>
<ol>
<li><p>Moments</p></li>
<li><p>Local and global characteristic</p></li>
<li><p>Energy of Image</p></li>
<li><p>Color Temperature</p></li>
</ol>
<p>What each of them represent in Image??</p> | 36,670 |
<p>Particles are suspended in a liquid medium at a concentration of 4 particles per mL. A large amount of the suspension is thoroughly agitated, and then 3 mL are withdrawn . Let $X$ be the number of the particles in the 3 mL. Answer the following:</p>
<p>a- The distribution of X is a Poisson distribution, what is its... | 74,042 |
<p>I noticed that in the Normal distribution, the probability $P(x=c)$ equals zero, while for the Poisson distribution, it will not equal zero when $c$ is a non-negative integer.</p>
<p>My question is: Does the probability of any constant in the normal distribution equal zero because it represents the area under any c... | 36,675 |
<p>I've studied machine learning and statistics only very briefly. I've used linear regression to solve problems with fixed sets of variables, but I'm not sure how to approach the following problem.</p>
<p>Given a bunch of tagged photos, I'd like to use the tags to estimate the probability that a specific object is co... | 74,043 |
<p>There is quite some content online interpreting odds in a logistic model with a dichotomous predictor. My problem is understanding coefficients when there are more than 2 levels for a categorical variable. How do you <em>define the odds</em> then?</p>
<pre><code>Data:
X is a single categorical predictor with 4 l... | 33,684 |
<p>Let's say you have $X$ coins, each with a differing probability of landing heads (e.g. coin 1 has 10% chance of landing heads, coin 2 has 20% chance of landing heads, etc.).</p>
<p>Now, let's say that you flip coin $i$ coin $Y_i$ times (each coin has a differing amount of flips). We know how many times each coin wa... | 74,044 |
<p>Is it plausible to have a positive coefficient with a negative marginal / impact effect after running multinomial logit model?</p> | 1,031 |
<p>I need to calculate the temporal trends for some climate variables with missing values. For example, last frost days defines as the last day of year with minimum temperature less than 0C. However, there are no any frost days in some years. </p>
<p>My data look like: </p>
<pre><code>lfd <- c(NA, NA, NA, NA, NA, ... | 74,045 |
<p>I am interested in developing a computational search of some types of non-coding RNAs (ncRNAs) on a new genome. I have some questions related to the nature of my experiment, because it is an exploratory study, and I can generate different results by applying different BLAST search strategies. The final output consis... | 48,340 |
<p>Let's say I ask a robot a question: "Why is partial differential equations no fun at all?" </p>
<p>Suppose the robot is stupid and categorizes my question inside the class of "cats" so it replies with: "Cats are fluffy and awesome."</p>
<p>So I reword my question over and over and sadly the robot keeps hitting the... | 36,680 |
<p>I was reading this <code>[paper][1]</code> related to sparse online gaussian processes. However, I didn't get how the denominator in the equation 1 was derived?<img src="http://i.stack.imgur.com/vr3dG.png" alt="enter image description here"></p>
<p>It was supposed to be P(D). I didn't get how the denominator was ob... | 36,681 |
<p>Suppose I have a dataset with the following information:</p>
<ul>
<li>N objects, each of which can be rated</li>
<li>The number of ratings per object is variable (raters are unidentified), e.g., there are 30 objects each with a unique id</li>
<li>Each row has the predicted rating, the actual rating, and the differe... | 6,464 |
<p>I'm trying to validate a series of words that are provided by users. I'm trying to come up with a scoring system that will determine the likelihood that the series of words are indeed valid words.</p>
<p>Assume the following input:</p>
<pre><code>xxx yyy zzz
</code></pre>
<p>The first thing I do is check each wor... | 36,683 |
<p>I have seen an apparently interesting quantity called the Bayesian complexity, which in this case is defined as $-2(\overline{\ln\mathfrak{L}} - \ln\mathfrak{L}_\mathrm{max})$. I am not sure what this is used for. I.e., what sorts of tests can be made on this quantity and what does it imply? </p> | 36,684 |
<p>I am currently working on a project in which I have to eliminate outliers from non-normally distributed data sets. </p>
<p>The data sets are subsets of a fairly large database (order of millions of observations) segmented into groups ranging from 30-200+ observations based on the type of product being looked at.</p... | 74,046 |
<p>I am using R for data analysis. R provides a <code>corr</code> function for calculating the correlation. <a href="http://www.statmethods.net/stats/correlations.html">This function</a> provides three different approaches/algorithms to estimating the <code>corr</code> which are Pearson, Spearman and Kendall. When shou... | 74,047 |
<p>I manipulate in R time series that can present <strong>revisions</strong>.
I use in general the package 'xts' but it doesn't support revisions.</p>
<p>Is there a package that deals with that?</p>
<p>Alternatively, is there a best practice to store and manipulate revisions?</p> | 36,687 |
<p><img src="http://i.stack.imgur.com/qTI9v.jpg" alt="enter image description here"></p>
<p>How can I calculate the mean of the first schema? I don't have the individual values of the sample. Std. Deviation (B) is 0.6441.</p> | 74,048 |
<p>This is an ill posed problem I'm faced with at work.</p>
<p>I have observations $X_i$, $i = 1,2,3,...N > M$. I need want to compute $S = \sum_{i=1}^M X_i$. Unfortunately, $M$ is random, and extremely noisy. It turns out, I have some rough "goodness" measures, $w_i$ for each of the $X_i$. That is, $w_i$ low,... | 74,049 |
<p>Violin players were asked to rate 5 violins from least to most rich on a <code>[0 1]</code>, <code>0.05-increment</code> scale, <code>most always = 1</code> and <code>least always = 0</code>. They were then asked to set a "limit of acceptability," i.e., to set a point along the scale above which violins are consider... | 74,050 |
<p>I am computing SVD on a matrix which is the empirical version of $E[XY^{\top}]$ for some $X \in \mathbb{R}^{m \times 1}$ and $Y \in \mathbb{R}^{n \times 1}$.</p>
<p>I am wondering if there are standard ways to preprocess $x_1,\ldots,x_l$ and $y_1,\ldots,y_l$ before doing that (other than subtracting the mean and di... | 162 |
<p>I have two models. First,
$$z=\alpha_1x+\alpha_2+\epsilon$$
and second,
$$z=\beta_1x+\beta_2y+\beta_3+\epsilon.$$</p>
<p>What factors affect whether $\alpha_1\approx\beta_1$? Note that I don't care how accurately either model predicts $z$. I only care about how similar the coefficient of the $x$ term is in both mo... | 36,691 |
<p>We have two time series: $X_t$ and $R_t$, and a model saying that $R_{t+1} = (\mu(X_t) - \frac{1}{2}\sigma^2(X_t))\Delta T + \sigma(X_t) \sqrt{\Delta T} \epsilon_t$,
where $\Delta T$ is given constant and $\epsilon_t$-s are independent normally distributed with zero mean and unit variance. Further we assume that the... | 74,051 |
<p>I'm only a linguist, so my knowledge of statistics is very basic.</p>
<p>I fitted a logistic regression model with R (with <code>lrm(formula, y=T, x=T)</code>), and when I use the option <code>validate(lrm)</code>, I get some statistics I don't really understand.</p>
<pre><code>index.orig training test optimis... | 1,722 |
<p>i try to implement a simple gaussian process regression in java. I almost got every step from the book <a href="http://www.GaussianProcess.org/gpml" rel="nofollow">http://www.GaussianProcess.org/gpml</a> .</p>
<p>With my implementation of algorithm 2.1 on page 19 i'm able to produce results but:</p>
<p>I have the ... | 74,052 |
<p>I want to create an equation that consists of two independent variables "duration" and "data_transferred", and one dependent variable "meeting_quality"</p>
<p>This is what I want:</p>
<p>meeting_quality would be good, if more data is transferred in less duration.</p>
<p>meeting_quality would be bad, if less data ... | 74,053 |
<p>I have a spreadsheet where the content is organized like that:</p>
<pre>
content | category1 | category2 | category3 | ...
_________|___________|___________|___________| ...
content 1| x | | x | ...
content 2| | x | | ...
...
</pre>
<p>How can I present this i... | 36,694 |
<p>In <code>R</code>, I would like to give multiline names to some data sets in <code>boxplot</code>, like this:</p>
<pre><code>boxplot(rnorm(10), rnorm(10, mean=2), names=c("Normal", "Shifted\n*"))
</code></pre>
<p>Here, the names seem to be aligned with their bottom lines, which causes the text to overlap with the ... | 36,695 |
<p>I wanted to create a bubble chart which means a scatter plot with a separate variable indicating diameter of bubble. Is there any way to use bubble then as pie chart? I would really like to do this in MS Excel but I just don't know whether it is possible. </p>
<hr>
<p>I have another problem with the code proposed ... | 36,696 |
<p>What is the PDF of the difference of two i.i.d Laplace distributed random variables?</p>
<p>I know that the difference of two i.i.d Normal variables is still the Normal distribution. Since the properties of the Laplace distribution are similar to the Normal distribution, I am guessing that the difference is also th... | 74,054 |
<p>I am comparing energy expenditure outputs from two devices that track physical activity in a free-living setting over 10 days. Doubly labeled water is the accepted criterion measurement for this, but 1) This technique only gives total energy expenditure and 2) I did not use this in my study...</p>
<p>Both of the de... | 74,055 |
<p>I've used chi-square analysis in school, but was absent for the lesson, and I never quite got the hang of it. I've been successful with it in the past, but now I'm trying to use percentage values, and I'm not getting the answers I'm expecting. I'm doing a survey and comparing my findings with national averages, but ... | 74,056 |
<p>If we have two variables A={20 values} and B={20 values} and we want to measure the correlation between these two variables. Lets assume that the first n values are highly correlated but the remaining m values are not correlated.
The overall correlation between A and B may not represent the importance of the relatio... | 36,700 |
<p>Do you know of any study where researchers have used Statistical Parametric Mapping for <strong>spatial data only</strong>? I found a lot of studies that used it for time-series analysis, but does this analysis work for data that don't share a time dimension? </p> | 74,057 |
<p>I have a time series $x_t$. If I use the transformation $u_t = log(x_t) - log(x_{t-1})$, my new time series $u_t$ has properties of white noise (random). I wonder whether there is any practical interpretation for $u_t$?</p>
<p>Thanks for your help.</p> | 74,058 |
<p>I am unclear about how to interpret the value of the Standard Error of the Mean (SEM) directly. For example, when a mean is reported as 5.00 + 0.50SEM, how do you directly relate the 0.50 to 5.00?</p>
<p>To quickly run through the basic theory concerning the standard error: </p>
<ol>
<li>The standard deviation (SD... | 48,370 |
<p>I've been working with spatial autocorrelation for a while and now I'm trying to move from more traditional estimators such as Moran's I or Geary's C to the new APLE estimator. I read Li's papers on APLE and also the reference on R-project. But I am still missing something very basic, as I still didn't understand so... | 48,374 |
<p>My question might be easy for most of you to answer. I am starting to learn statistics and coding in R so my questions are on the basic level.</p>
<p>I have a dataset of (two groups, replicates). My data is split based on the groups so I have 24 samples in group 1 and 20 samples in group 2. My data has replicates. ... | 74,059 |
<p>I have a logit model and am trying to understand and compare the predicted and observed values generated by the model. Let's say data set had 100 values and I generate all the predicted probabilities, and then I find the actual probabilities from the data set.</p>
<p>If I'm comparing the predicted vs observed value... | 74,060 |
<p>I have a lot of data (gigs) that may be useful in predicting equity prices. I can import these as a series of features (columns) in a table where the companies are rows. I have time series information too.</p>
<p>I have some machine learning experience but no experience as a trader.</p>
<p>Is there some software o... | 44,147 |
<p>I read that the k-means algorithm only converges to a local minimum and not to a global minimum. Why is this? I can logically think of how initialization could affect the final clustering and there is a possibility of sub-optimum clustering, but I did not find anything that will mathematically prove that.</p>
<p>Al... | 44,377 |
<p>Could anyone suggest the best method to predict the time gap between two events?</p>
<p>For example, given that diabetics are at higher risk of developing hypertension, I would like to predict the time gap until patients develop hypertension after being diagnosed with diabetes. </p>
<p>I will have both time depend... | 74,061 |
<p>I have been using successfully DBNs for classification for MNIST and some other tasks.</p>
<p>I was thinking of doing dimensionality reduction before training, in order to boost performance. However, when I tried out using the output of PCA to train a deep belief network the results were quite bad.</p>
<p>I unders... | 74,062 |
<p>I am a little bit confused about the machine learning outcomes on my dataset. I would be grateful if anyone can enlighten me on this:</p>
<p>When features are statistically different between two groups, shouldn't the machine learning able to predict the right class with a reasonable accuracy? The data consists of ... | 36,705 |
<p>Suppose I have a big online company, and many of my customers churned (i.e. they were paying, and then stopped). My goal is to understand why each of them churned.</p>
<p>First I identify the complete set of reasons for churning, $H_1,\ldots,H_n$. E.g. "the website is confusing", "the customer lost interest", etc.
... | 74,063 |
<p>In calculating the pseudoinverse of a matrix $A$, of size (m,n), I need to choose a tolerance threshold for the eigenvalues. I'm trying to understand how I should pick this. Matlab default is to use the $norm(A)*max(m,n)*eps$, where the norm is norm-2 and the eps is the machine epsilon. Any ideas as to why this is t... | 33,239 |
<p>I have a dataset that includes variables about customer income levels. The income was collected in binned fashion (<code>Which range describes your income? 0-25k, 25k-50k,...</code>). My question is how best use this for modeling using <code>glmnet</code> and <code>gbm</code> packages in <code>R</code>.</p>
<p>I ... | 74,064 |
<p>I am interested in fitting a Poisson/negative binomial distribution to estimate the number of times a phenomenon happens within a period, let's just say 10 years. I can count the events from monthly reports, but unfortunately, there are reports missing. So for one sample, I might have 120 observational slots, but fo... | 74,065 |
<p>I am using the <code>flexmix</code> package to estimate latent class multinomial logit models in R. In choice theory, there can be variables associated with the alternative (generic) or that vary with the agent (alternative-specific).</p>
<p>The <code>nnet</code> package that underlies <code>FLXMRmultinom</code> ca... | 36,709 |
<p>I need to predict with a simple model if a bank customer is still active.</p>
<p>I have some information like the date of the last meeting with the customer, but some of them didn't have any meeting with their advisor.</p>
<pre><code>Customer_Id | Last_meeting_date (in days from now) | Gender |...
A ... | 36,710 |
<p>I have one categorical dichotomous dependent variable (yes/no - retention of newly learned words) and two independent variables - both are categorical. One independent variable is "delay between exposure and test" and has two levels (short time delay/week time delay). The other IV is "word type" and relates to the... | 33,244 |
<p>I need help with the following question:</p>
<p>Consider $m$ observations $(y_1; n_1); ... ; (y_m; n_m)$, where $y_i \sim Bin(n_i; θ_i)$ are binomial variables.
Assume that $θ_i \sim w_1Beta(α_1; β_1) + w_2Beta(α_2; β_2)$ are mixture from two Beta distributions $(w_1 + w_2 = 1)$. </p>
<ul>
<li>Derive a Laplace ap... | 48,384 |
<p>I have a huge dataset (millions of rows, thousands of columns) and <code>glmnet</code> Lasso regularised regression is too slow.</p>
<p>I am wondering what other libraries there are that try to implement regularised linear model estimation extremely efficiently? I don't necessarily need a distributed solution (it c... | 33,249 |
<p>I have a data set and I want to examine an hypothesis in there and probably Network Analysis should prove or reject my theory.</p>
<p>I have a list of products and a group of people who give the product to each other. Anyone can sell it to another in any price he want (hopefully someone will buy it).</p>
<p>So, im... | 74,066 |
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