Matt J

Last seen: Today

6.754 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Submitted

spatialgraph2D
Creates a graph object with 2D spatial locations associated with the nodes

alrededor de 5 horas ago | 14 downloads |

Answered
Deleting within .mat file
I don't remember that ever being possible through the Matlab GUI, but attached is a MEX file that can do it. rmvarMatfileMEX('a...

alrededor de 6 horas ago | 0

Answered
Concatenate the produced arrays from a for loop?
Mean=nan(50,3); for j = 1:50 fname = sprintf('test (%d).bmp',j); image4d = imread(fname); Mean...

alrededor de 7 horas ago | 0

| accepted

Answered
Big-O Complexity analysis for "fmincon"
It depends on the objective function and constraints. For a qudaratic function and no constraints, the number of iterations is O...

alrededor de 11 horas ago | 0

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3D interpolation at points
griddata(X,Y,Temp,xp,yp)

alrededor de 11 horas ago | 0

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Find the intersection between object boundaries and a line
B=cell2mat(bwboundaries(bw,8,'noholes')); [x,y]=deal(B(:,2),size(bw,1)+1-B(:,1)); [d,loc]=min( abs( slopeInv.*(x - Target...

alrededor de 11 horas ago | 0

Answered
Minimum value ineach column
We don't know what columnA is in the code that you've shown. It would have to be a vector with the same number of columns as A f...

alrededor de 19 horas ago | 0

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Answered
Optimal way to create a large matrix from smaller chunks
One way is to do a dry run to see how big the matrix is supposed to be: Znlm=matrixGenerator(rand(5,1),rand(5,1),30,10,10); ...

alrededor de 20 horas ago | 0

Answered
Input not numeric? error
AdaptFFTCleand is a 4000x2 matrix of positve and negative real numbers. It isn't possible that AdptFFTCleand is a numeric matri...

1 día ago | 0

| accepted

Answered
FFT along third dimension
They are equal, >> isequal(g3, fft_3d ), isequal(g3 , ff_3d ) ans = logical 1 ans = logical 1 al...

1 día ago | 0

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Fit a broken, wavy object outline in image processing
A smoothing spline may work well, https://www.mathworks.com/help/curvefit/csaps.html#mw_94a487bc-e854-4919-929d-05af98ae0519 I...

1 día ago | 0

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Concatenate x amount of matrices
See BLKDIAG https://www.mathworks.com/help/matlab/ref/blkdiag.html

1 día ago | 0

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Curve fitting with a constrained y value to Zero
Using lsqlin, x0=21.1; x = [4.4 37.8 54.4 ].'; y = [2.367224698 -1.857318083 -3.276015126].'; p=lsqlin(x.^[2,1,0],y,[]...

2 días ago | 1

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Non-linear fitting for more than three variables
When I try to run the script ,many errors prevent the running.Is this script correct for running? No, you need to be using .* t...

2 días ago | 0

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From MATLAB to Python
Below is a illustration of what i think this code means It's not clear which column corresponds to which variable in your code....

2 días ago | 1

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Wrong Hessian output in fminunc
Another solution would be to use standalone routines for numerical gradient and hessian estimation https://www.mathworks.com/ma...

2 días ago | 0

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Wrong Hessian output in fminunc
Just run fmincon (twice) with no constraints. Running a second time is important, because the hessian output is not the Hessian ...

2 días ago | 0

Answered
spline with non monotonic axis
t = 0:100; x= sin(0.2*t); y = cos(0.6*t); tq = 0:.25:100; xy = spline(t,[x...

4 días ago | 0

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Usage of structure as input of a function. Is it efficient ?
The thing is that if I stop using structures, I'll have gigantic function calls to write. And if I stop using functions, I'll ha...

4 días ago | 3

Answered
How do I assign values from 1D arrays to 4D arrays efficiently
I do this so I can use vectorization to greatly speed up the performance of my calculations by using element-wise operations. Ho...

6 días ago | 1

| accepted

Answered
lsqnonlin is only giving the initial point
I don't know if the solution is what you were expecting, but this gives exitflag 1, la=[39.873297 39.872124 39.869953 39.864596...

6 días ago | 1

| accepted

Answered
Find the Argmin of a vector
You should have avoided naming the variables that way, and should have used (for example) a cell array. Indeed. Here's an examp...

6 días ago | 0

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Answered
Recover matrix Z from XZX', Z es symmetric and n-by-n, while X is k-by-n where n>>k
In the case where k truly is <<n, you can use my KronProd class to get the minimum norm solution https://www.mathworks.com/matl...

7 días ago | 0

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Sum of m- fold convolution
if you write the expression in the frequency domain, it just becomes a big polynomial...

7 días ago | 0

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Why is memory reduced for an identical copy of a sparse array?
Are you sure you have to worry about it? According to what I'm seeing (in R2019a,R2020a), the extra 16 bytes occurs only anomolo...

7 días ago | 0

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standard deviation and mean across specific columns of a 3D matrix
If the idea is to average along rows 2 through 5 in every slice, you would want this, MmtxT1 = mean( mtx([2 3 4 5],:,:) , 2); ...

7 días ago | 0

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Answered
How to increase memory available for arrays?
A simple solution might be to close other applications that might be consuming RAM. For example, closing Microsoft Outlook freed...

8 días ago | 0

Question

EVALIN cannot execute a return?
I am trying to create a function that aborts whatever mfile is currently executing after issuing a warning. I see no way of avoi...

8 días ago | 2 answers | 0

2

answers

Answered
make vectors same length
One way, collection = {acc,gyr,mag}; minlen = min(cellfun('length',collection)); clipped=cellfun(@(z)z(1:minlen),collecti...

8 días ago | 1

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Answered
Can I change degrees to radians by simply changing from sind to sin?
cos and sin will assume the input angles are measured in radians. If theta is in degrees, you must convert to radians in order t...

9 días ago | 1

| accepted