Alfonso Nieto-Castanon

Last seen: 6 months ago | Active since 2012

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http://www.alfnie.com http://www.conn-toolbox.org

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Simulating the Central Limit Theorem with Non Uniform Distribution in MATLAB
x = mean(rand(100,1000)); hist(x);

9 years ago | 2

Answered
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 ...

9 years ago | 1

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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...

9 years ago | 1

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Answered
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...

9 years ago | 1

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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...

9 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...

9 years ago | 0

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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...

9 years ago | 1 answer | 0

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Storing 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)); ...

9 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...

9 years ago | 0

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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...

9 years ago | 0

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Answered
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...

9 years ago | 0

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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 "...

9 years ago | 1

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Answered
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...

9 years ago | 2

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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...

9 years ago | 1

Answered
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...

9 years ago | 0

Answered
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...

9 years ago | 2

Answered
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...

9 years ago | 0

Answered
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))));

9 years ago | 0

Answered
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')));

9 years ago | 0

Answered
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...

9 years ago | 3

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Answered
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...

9 years ago | 0

Answered
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...

9 years ago | 5

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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...

9 years ago | 6

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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 ...

9 years ago | 1

Answered
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...

9 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,...

9 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#...

9 years ago | 1

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Answered
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...

9 years ago | 0

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

9 years ago | 0

Answered
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...

9 years ago | 2

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Alfonso Nieto-Castanon

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