# Alfonso Nieto-Castanon

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**Content Feed**

Simulating the Central Limit Theorem with Non Uniform Distribution in MATLAB

x = mean(rand(100,1000)); hist(x);

6 years ago | 2

SVD of symmetric complex matrix is giving an unexpected result.

Well, yes, they are "equal" up to a constant pure-phase term, which is always arbitrary in SVD (for any left and right singular ...

6 years ago | 1

| accepted

How do I make the chi2rnd(size) Matlab function faster for big matrices?

storing the chi2rnd(2048, 1000000) results require about 16Gb of memory, perhaps the extra time is due to memory-swapping rather...

6 years ago | 1

| accepted

Check if a graphics object is visible to the user

While it is simple to check which object is visible, e.g.: function ok = isvisible(handle) ok = true; while ok&&~isequal...

6 years ago | 1

| accepted

How to import Excel data from a spreadsheet with cross-file references?

I clearly would not recommend this as a first choice, but if nothing else works then perhaps you can simply have Matlab open, sa...

6 years ago | 1

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how to average the close points ?

If you do not have "lines" of close points (the transitiveness issue that Walter mentioned), a simple and quick way to do this c...

6 years ago | 0

Question

solving a matrix exponential equation

I know this is perhaps a "methods" question rather than a purely "Matlab" question, but does anybody know or could point me towa...

6 years ago | 1 answer | 0

### 1

answerStoring blocks of matrix data into a cell array

You may use <http://www.mathworks.com/help/matlab/ref/mat2cell.html mat2cell> for that. For example: rows = find(any(X,2)); ...

6 years ago | 1

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Generate arrow keys in MATLAB gui

The cdata approach is probably simpler. First check that variable rarrow_img contains the correct 3D matrix format (see th...

6 years ago | 0

| accepted

how do I calculate t-value when I only know the mean of 10 and 95% confidence interval. I do not know sample size.

There are some subtleties depending on how your 95% confidence interval was computed, but typically: CI = tinv(.975,N-1)*s...

6 years ago | 0

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Reducing dimensionality of features with PCA

If you use: [coeff,score] = pca(M); Comp_PCA1 = score(:,1); where M is a (300 by n) matrix of voxel timeseries, and you...

6 years ago | 0

Shortest Path in a 3D Matrix

If you do not really care too much about the 'uniqueness' issue brought up in the comments, and just want to consider a single "...

6 years ago | 1

| accepted

Current figure handle ignoring my open figure

most likely reason is that your figure has its _HandleVisibility_ property set to 'off' or 'callback' (so its handle is partiall...

6 years ago | 2

| accepted

how to achieve a smooth transition of a straight line trajectory into a semi circle trjaectory

Your problem definition is unclear, but I would probably try setting this as an optimization problem where you try to optimize s...

6 years ago | 1

Can any one suggest me how to make a large matrics positive definate.

the matrix B defined as: B = (A+A')/2 + lambda*speye(size(A,1)); will have eigenvalues eig(B) equal to real(eig(A))+lambd...

6 years ago | 0

Random Gaussian Surface Generation

You may use something like: N = [500 500]; % size in pixels of image F = 3; % frequency-filter width [X,Y] = nd...

6 years ago | 2

Why does the time scale for a ifft depend on the frequency interval of the frequency signal?

If you have a signal x with N samples acquired at a sampling rate Fs, then: 1) The time axis of your vector x (the time ass...

6 years ago | 0

Finding the "center integers" of an array

x = [1 2 3 10 11 12 15 16 17 20 21 22 23 24 30]; y = cellfun(@mean,mat2cell(x, 1, diff(find(diff([nan x nan])~=1))));

6 years ago | 0

Finding the "center integers" of an array

x = [1 2 3 10 11 12 15 16 17 20 21 22 23 24 30]; y = x(floor(convn(find(diff([nan x nan])~=1),[1 1]/2,'valid')));

6 years ago | 0

Stop the execution of a function with a push button (GUIDE)

See <http://www.mathworks.com/matlabcentral/answers/142147-gui-push-button-problem this related question> Using drawnow withi...

6 years ago | 3

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How to calculate a 2D rotation vector with PCA?

find the angle between the first column of PCA1 and the first column of PCA2 (hint: cos(angle(a,b))*norm(a)*norm(b)=a'*b) and bu...

6 years ago | 0

Implementing a sine wave with linearly changing frequency

someone deleted his own answer including my own comments to it so, just in case these are interesting to anybody else, I am repe...

6 years ago | 3

Implementing a sine wave with linearly changing frequency

the formula: sin( 2*pi*f(t)*t ) does not result in the desired sine wave with time-varying frequency. Rather the appropri...

6 years ago | 4

How to run a repeated-measures t-test in Matlab to determine whether you can reject the null hypothesis.

use <http://www.mathworks.com/help/stats/ttest2.html ttest2> for a two-sample t-test (the two conditions are from two different ...

6 years ago | 1

F-Test for difference between coefficients

help <http://www.mathworks.com/help/stats/generalizedlinearmodel.coeftest.html coefTest> and use a contrast H that compares t...

6 years ago | 3

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How to get around out of memory issue

If your end-goal is to actually compute that entire 80000 x 80000 matrix, and you do not have enough memory to keep that matrix,...

6 years ago | 0

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Keep GUI functions running when opening an uigetfile Dialog?

No, as far as I know uigetfile will create a modal window (see <http://www.mathworks.com/help/matlab/ref/figure-properties.html#...

6 years ago | 1

| accepted

Implementing Breadth first search using connectivity matriX

See <http://www.mathworks.com/help/matlab/ref/dmperm.html _help dmperm_> If I am interpreting correctly, something like the f...

6 years ago | 0

From inline to anonymous function

if you have the symbolic toolbox: g = matlabFunction(sprintf('[%s; %s]', dx1dt, dx2dt)); otherwise your best bet is proba...

6 years ago | 0

Sum two cells and write to a third cell

Probaby a loop is going to be fastest, e.g.: for n=1:numel(A) A{n}(:,1)=B{n}(:,1)+C{n}(:,1); end but if you reall...

6 years ago | 1

| accepted