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Matt J


6,049 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
How to check if an entire column of string variables can potentially be converted to numerical values?
all(48<=yourMatrix(:) & yourMatrix(:)<=57)

2 hours ago | 0

Answered
Calculating statistical functions for a structure array which each cell has a different size
A structure array doesn't have "cells" and doesn't look like that. I assume you really mean your data is a cell array, in which ...

16 hours ago | 0

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Answered
For loop for summation
R= zeros(size(y)); N= -500:500; for j=1:numel(N) n=N(j); R = R + f(n).*y.^(-n); end

16 hours ago | 0

Answered
Produce matrix B from matrix A
B=[A(1,2:3); A(1:2,1).'; 10 11]

16 hours ago | 0

Answered
How to check if an entire column of string variables can potentially be converted to numerical values?
~any(isletter(yourMatrix(:)))

16 hours ago | 0

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Answered
Superimposing matrices in a specific location
Something like this, perhaps: [i0,j0]=deal(700,850); %target location [I,J,S]=find(smallMatrix); result = largeMatrix + ...

16 hours ago | 0

Answered
Trouble calculating column mean from a matrix - using different indices for each row
[m,n]=size(myMatrix); %Edited e=1:n; mask=VariableIndex1(:)<=e & e<=VariableIndex2(:); result=sum(myMatrix.*mask,2)./sum(...

1 day ago | 0

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Answered
Kron error when dealing with sparse gpuarrays
You may want to look at, https://www.mathworks.com/matlabcentral/fileexchange/25969-efficient-object-oriented-kronecker-product...

1 day ago | 0

Answered
Use several pools of workers in a parfor loop
Your terminology is a bit confusing. There is only ever 1 pool of workers, but each worker may use multiple cores and the entire...

2 days ago | 0

Answered
How to write your own function for infinity-norm of a matrix
To sum the rows of any matrix A, sum(A,2)

2 days ago | 0

Answered
Fastest way to substitute elements in a matrix at given positions?
idx = sub2ind([n,m], repmat((1:n).',1,l) ,B); A(idx)=value;

3 days ago | 0

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Answered
Matlab fmincon(function based) optimality issue :: constrained nonlinear optimization
But , in my case, optimality is very large even though the objective fval is converge (please check img.) Your plots are uninte...

3 days ago | 1

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Answered
How to use fzero in a loop to obtain the first 3 positve solutions for cos3x=sin3x?
It seems like a strange homework problem, since it is so easily solved analytically. Well, assuming we play dumb to that, you ne...

3 days ago | 0

Answered
gap filling with liner interpolation
A=xlsread('data.xlsx'); I=A==-9999; J=find(~I); B=A; B(I)=interp1(J,A(J),find(I));

3 days ago | 0

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Answered
what is the source code of gridinterpolant function? what is the algorithm?
No, there is no way to see the souce code for griddedInterpolant.

4 days ago | 1

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Answered
Sum of a series?
Hint: >> 1./(1:5) ans = 1.0000 0.5000 0.3333 0.2500 0.2000

4 days ago | 0

Answered
Rasterize a triangle in 3-D space.
One way is to use vert2lcon, https://www.mathworks.com/matlabcentral/fileexchange/30892-analyze-n-dimensional-polyhedra-in-term...

7 days ago | 0

Answered
How to find the x and y coordinates corresponding to a given value of f(x,y)?
maxval=max(f(:)); [xmax,ymax]=find(f==maxval);

7 days ago | 1

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Answered
Why do results of fft() on a matrix differ from fft() on one row as a vector?
The same dicrepancy exists with most Matlab functions that do operations along rows or columns. Here is the same test replacing ...

7 days ago | 1

| accepted

Answered
why the script show wrong output can you help me?
tplot=[0:0.01:2*pi]; x=double(subs(pos,tplot)); y=double(subs(v,tplot)); z=double(subs(a,tplot)); p=plot3(x,y,z);

7 days ago | 0

Answered
From a set of curves, how to find the one that the "most similar" to the reference curve?
The code below uses fminspleas https://www.mathworks.com/matlabcentral/fileexchange/10093-fminspleas to do a simple 1D registr...

8 days ago | 0

Answered
Sparse gpuArray accumulation in for-loop
I would guess that your Kernel matrix is becoming less and less sparse as you accumulate until its memory consumption is growing...

8 days ago | 0

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Answered
Optimization with loops Error in optim.problemdef.OptimizationProblem/solve
I believe it will probably involve multiplication by some upper triangle matrices of 1 with some other operations but I cannot w...

8 days ago | 0

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Answered
Find the points on circumference of a circle
Okay Considering 5 pixels + or - for the inaccuracy to find all the x,y, points on the circumference; how can I find even those....

8 days ago | 0

Answered
Matlab code to split an image into a square grid of square blocks
This uses mat2tiles (Download) A=mat2tiles( imread('cameraman.tif'), [32,32]); [m,n]=size(A); B=cell2mat(A(randperm(...

9 days ago | 0

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Answered
Find matching points from two coordinate systems
If the shear component of the deformation isn't too strong, the matchpoints function defined below might work. It will sort the ...

10 days ago | 0

Answered
Find cycles in an undirected graph
Because this sounds like a generally useful thing, I cooked up the attached polyregions class to do the partitioning that you de...

10 days ago | 1

| accepted

Answered
Function handle for combinations of calculations
One way: N=5; [G{1:N}]=ndgrid([-1,1]); G=reshape(cat(N+1,G{:}) , [],N); and now the combinations are given by ...

10 days ago | 0

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Answered
I need help with this MATLAB question
I know how to get user input but how do i get it through a pop up box? One option is inputdlg, https://www.mathworks.com/help...

10 days ago | 1

Answered
How do I reorder unequal columns in a field
yourStruct.Vs=permute(yourStruct.Vs,[2,1,3]);

11 days ago | 0

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