Jeff Miller

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491 total contributions since 2013

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Answered
How can I evaluate characteristic functions in MatLab?
It seems like your question contains its own answer: mu = 1; sigma = 1; t = -2.5:0.01:2.5; cf = exp(i*mu*t - sigma^2*t.^2/2)...

4 dagar ago | 1

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How to perform 1way-ANOVA with matrices
manova might be a better approach, since it allows you to combine information from all three variables (x,y,z) into a single tes...

4 dagar ago | 1

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Passing Covariance Matrix in Likelihood Maximization
Sometimes this kind of problem can be solved by adding code within the LogLik function to make sure that a legal (i.e., positive...

8 dagar ago | 0

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how can i calculate z^2 distibution?
The distribution of z^2/a^2 is a chi-square with 1 df.

9 dagar ago | 0

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How can I get randperm to return a permutation of a vector that has no entries at their original positions?
I don't think randperm can do that by itself, but I think this would work for an even number of items in the original vector: o...

9 dagar ago | 0

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R code to matlab, or simply generating a zero mean gaussian and finding the covariance matrix
x=normrnd(0,1,5000,1); v=normrnd(0,0.3,5000,1); y=0.5*x+v; cov=mean(x.*y)-(mean(x)*mean(y)); cov s=cov*(sqrt(var(x)))*(sqrt...

11 dagar ago | 0

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Generating a histogram from lognormally distributed data
What about something like this: mu = 0.015; % mean particle size sg = 1.6; % standar...

12 dagar ago | 1

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How to integral a pdf of a continuous random variable to calculate its entropy
Try this: pd = makedist('beta','a',50,'b',40); fun = @(x) pdf(pd,x) .* log( pdf(pd,x) ); H = -integral(fun,0,1)

13 dagar ago | 0

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Fit data to beta distribution
There is information here about how to fit a univariate distribution from an empirical CDFs with MATLAB. Unfortunately, it is a ...

14 dagar ago | 0

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how to create a pdf function of two variables that are in different uniform distribution
If they are independent then the joint pdf is the product of the marginal pdfs, so in this case pdf(x,y) = 0.01

14 dagar ago | 0

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Calculate Exponetial Moving Covariance
Not really a hand, but maybe some hints...Let's say you have variables x and y, and you want the exponentially weighted rolling ...

17 dagar ago | 0

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Answered
Select sample from an array
Maybe this: ints = [2:7:259 3:7:259 4:7:259 5:7:259]; srtints = sort(ints); X1 = x(:,srtints);

17 dagar ago | 0

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Answered
Kruskal-Wallis test with very small p-values
p values can be anywhere between 0 and 1, depending on your data. a tiny p value like that is telling you that you would very r...

18 dagar ago | 0

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Fitting a multivariate Gaussian distribution on a histogram
There isn't really a universal answer to "which distribution fits best", because there are an infinite number of different distr...

21 dagar ago | 0

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Answered
How to index through variable list in a table after doing calculation with each variable
myVars = {'Var1name' 'Var2name' 'Var3name'}; % list the names of the variables you want for iVar=1:numel(myVars) thisColu...

23 dagar ago | 1

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How to obtain the standard error for each of the fitted parameters
The notion of a standard error assumes some kind of random sampling. For example, the standard error of your 'b' parameter refl...

23 dagar ago | 0

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sqlite foreign key constraint not enforced
In case anyone else is interested, here is the answer from MATLAB technical support: This [is] a bug in executing PRAGMA querie...

24 dagar ago | 0

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Weird fitting result from using 'ksdensity'
Try histogram(x,'Normalization','pdf')

24 dagar ago | 0

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How to plot a spatial correlation with a p-value threshold?
After you get X (bottom of your first code segment): rCrit = 0.312; % Based on N=40 and alpha = 0.05, 2-tailed, from a table of...

ungefär en månad ago | 0

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Answered
double truncated data sample
This is pretty ugly, but I think will do what you asked for: function [x]=generate_sample(n,eta,beta,theta,t1,t2) % ...

ungefär en månad ago | 0

Question

sqlite foreign key constraint not enforced
My question is how to get MATLAB's sqlite databases to enforce foreign key constraints. Here is a minimal working example illus...

ungefär en månad ago | 1 answer | 0

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How to use least square fit in MATLAB to find coefficients of my polynomial?
% It sounds like you have data arrays like these: nPoints = 100; H = rand(nPoints,1); C = rand(nPoints,5); % If so, comput...

ungefär en månad ago | 1

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Answered
How to remove effect of "in" predictors on "out" predictors in stepwiseregression?
One way to think of it is that the "out" predictors will only improve the fit of the regression model if they bring in some new ...

ungefär en månad ago | 1

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How to fit data in exponential fit (R = exp(-q*D)) and find coefficient "q" using Maximum Likelihood Estimate (MLE)?
As I read this question, it is about fitting a model rather than a distribution, so I don't think mle is appropriate. Instead, ...

ungefär en månad ago | 0

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Multivariate analysis of variance in Matlab
You need to arrange your data in a table with one row per individual group member. For example, your first group seems to have ...

ungefär en månad ago | 1

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Selecting a "random" element from an array with each element having it's own weighting
% Wts is your vector of weights. Wts = Wts / sum(Wts); % make sure they sum to 1 cumPrs = cumsum(Wts); % cumPr is the cumula...

ungefär en månad ago | 0

Answered
Help fitting data to an implicit equation
I would suggest using fminsearch. The error function to be minimized would be something like: function thiserr = err(x,y,t) ...

ungefär 2 månader ago | 0

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Answered
Chi-squared for multiple groups
The crosstab function will do this--it is not limited to 2x2 tables. Example: % Make up example data for 200 participants, codi...

ungefär 2 månader ago | 0

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using mle in matlab
One problem is that mle's search function (fminsearch) may try negative parameter values, in which case your pdf function return...

ungefär 2 månader ago | 0

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ttest2 with a group describing independent values (statistics)
No, it is not possible to use ttest2 as you suggest. Your design has 2 factors: gender and time (day/night) with repeated measu...

2 månader ago | 1

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