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Matt J


Last seen: Today |  Active since 2009

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Professional Interests: medical image processing, optimization algorithms

PLEASE NOTE: I do not read email sent through my author page. Please post questions about FEX submissions in their respective Comments section.

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Answered
Getting different results from function handle & syms for a same equation. How to avoid it?
The results are different because the polynomial coefficients are different: >> sym2poly(P)-coeffs' ans = 1.0e-04 * ...

ongeveer 3 uur ago | 0

Answered
How to "quicksave" a file in app designer?
The 3rd argument to uiputfile should end with a path separation character: [file,path] = uiputfile(".mat","Save AnimTronics Sys...

ongeveer 4 uur ago | 0

Answered
how convert the vector to matrix ? unknown number of columns
No, the solution is ill-defined. Another result with the same number of rows is: A=[1 2 3 4 5 6 7 8 9]

ongeveer 13 uur ago | 0

Answered
Applying vectorization techniques to speedup the performance of dividing a 3D matrix by a 2D matrix
Another idea. clc; clear all; % Test Data % I'm trying to remove the for loop for j in the code below N = 10; M = 10; Nx...

ongeveer 16 uur ago | 1

Answered
Applying vectorization techniques to speedup the performance of dividing a 3D matrix by a 2D matrix
On the GPU (i.e. if A and b are gpuArrays), the for-loop can be removed: Uhat = permute( pagefun(@mldivide,A,reshape(b,[],1,Nx)...

1 dag ago | 0

Answered
Finding the vertical offset of a gaussian fit
This File Exchange routine does gaussian+constant fitting: https://www.mathworks.com/matlabcentral/fileexchange/69116-gaussfitn...

1 dag ago | 0

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Answered
How to set a custom equation to fit 5 points in space by fitsurface?
I can't find "fitsurface" in the Mathworks documentation, but the fit is easy enough to do algebraically. x=x(:); y=y(:); z=z(:...

2 dagen ago | 0

Answered
Why is x(:) so much slower than reshape(x,N,1) with complex arrays?
The following simple test seems to support @Bruno Luong's conjecture that (:) results in data copying. The data of B1 resulting ...

2 dagen ago | 1

Answered
Is it possible to correctly perform a multi-dimensional FFT on a 1D linearised version of a 3D array?
Reshaping to and from 3D format should not add significant cost: Nx = 256; Ny = 256; Nz = 128; N = Nx*Ny*Nz; A0 = rand(N,1)...

3 dagen ago | 0

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Question


Why is x(:) so much slower than reshape(x,N,1) with complex arrays?
The two for loops below differ only in the flattening operation used to obtain A_1D . Why is the run time so much worse with A_3...

3 dagen ago | 3 answers | 2

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answers

Answered
see the 3d image and see the coordinates while moving the mouse over the image
You can use imshow() to display any particular slice of the image and then use the axis datatip button to get the in-slice 2D co...

4 dagen ago | 0

Answered
How do i find the coordinates of a boundary
How about simply, [m,n]=size(Image); I=boundary(:,1); J=boundary(:,2); corner1 = [1, max(J(I==1))]; %row/column coordinat...

4 dagen ago | 0

Answered
How to Draw an ellipsoid between two 3d coordinates
Another way would be to use the ellipsoidalFit.groundTruth method in this File Exchange submission. https://www.mathworks.com/m...

4 dagen ago | 0

Answered
Trying to count the number of pixels in an image over a specific RBG value
results.area=nnz(imstd>90);

4 dagen ago | 0

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Answered
Normally distributed random numbers with fixed sum
Why not simply, x(1:N-1)=randn(1,N-1); x(N)=fixedValue-sum(x(1:N-1))

4 dagen ago | 0

Answered
Only analyze what is outlined in black in an image
If you have a binary mask of the circles, you can just do numBlack = nnz( circles & ~BW ); numWhite = nnz( circles & BW);

4 dagen ago | 0

Answered
If the quadprog problem is infeasible, how i can solve it with a certain tolerance?
It never really makes sense to have more equality constraints (here 36) than you do unknowns ( here 6). In order for the problem...

6 dagen ago | 0

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Answered
How to construct a "ones" matrix with zero blocks in the diagonal
repelem(1-eye(4),4,4)

6 dagen ago | 1

Answered
Iterative solution of non-linear equation with a provided guess value?
You could use fzero's OutputFcn option https://www.mathworks.com/help/optim/ug/fzero.html#btn3z5s-options to access the sequen...

6 dagen ago | 0

Answered
Iterative solution of non-linear equation with a provided guess value?
Using fsolve() instead of fzero(), you could solve the problem as a system of two equations in two unknowns. The two unknowns ar...

6 dagen ago | 0

Answered
Failure in initial user-supplied nonlinear constraint function evaluation
One problem: nonlcon = @simple_constraint; There is no function called 'simple_constraint' in your attached script. There is a...

7 dagen ago | 1

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Answered
for loop for permutations of for length of array
List=nchoosek([a,b,c],2); for i=1:size(List,1) p1=List(i,1); p2=List(i,2); ... end

8 dagen ago | 1

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Answered
How do I use an if-else structure inside a for loop to investigate if each component of a row vector is inside or outside the boundaries?
Hint: for i=1:numel(vec) v=vec(i); end

8 dagen ago | 0

Answered
2*2 Matrix factorization/decomposition
I also found out what I wanted may have something to do with PLU(permuted lower upper decomposition), but am clueless to how to ...

8 dagen ago | 0

Answered
How can I call a script within a for loop, looping over multiple files?
result = scriptname(ID{nSubject},Visit{nVisit});

9 dagen ago | 0

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Answered
I am trying to find the exact distance of a curvy line.
Why not as follows? I2 = imread('image.jpeg'); blue=bwareafilt( I2(:,:,1)<=50 & I2(:,:,2)<=50 & I2(:,:,3)>=200, 1); Len...

9 dagen ago | 0

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Answered
Number of branches per branch point
Perhaps as follows: k=ones(3); k(5)=0; neighborCount=conv2(double(BW),k,'same'); neighborCount=neighborCount.*(neighborCo...

9 dagen ago | 0

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Answered
Rank deficient error.
Are you attempting to do matrix division? if not use ./ instead.

9 dagen ago | 1

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Answered
Merge struct with matrix
You cannot avoid a for-loop altogether, but you can avoid writing your own for-loop as follows: tmp=num2cell(modelOutputSignal,...

9 dagen ago | 0

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Answered
Unable to detect Iris boundary using imfind circles
Increasing the lower radius bound as suggested by @Jonas as well as increasing the sensitivity setting seems to help: A=any( im...

9 dagen ago | 0

| accepted

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