Matt J

Last seen: Today

6,748 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
3D interpolation at points
interp1 will do it. Example, [xp,yp]=deal((1:6).'); xy = interp1([xp,yp], 1:0.5:6) xy = 1.0000 1.0000 1.50...

10 hours 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...

10 hours ago | 0

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

18 hours 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...

20 hours ago | 0

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

20 hours 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,[]...

22 hours 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...

22 hours 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....

23 hours 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...

23 hours 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 ...

1 day ago | 0

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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...

3 days 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 days ago | 3

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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...

5 days ago | 1

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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...

5 days ago | 1

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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...

5 days 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...

6 days 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...

6 days 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...

6 days ago | 0

Answered
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); ...

6 days 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...

7 days 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...

7 days ago | 2 answers | 0

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answers

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

7 days 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...

8 days ago | 1

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Answered
How to use linear and quadratic programming to optimize w to solve the following problem
This looks like a direct application of lsqlin https://www.mathworks.com/help/optim/ug/lsqlin.html

8 days ago | 0

Answered
count number of indices
Using group1s from the File Exchange https://www.mathworks.com/matlabcentral/fileexchange/78008-group1s col2=arrayA(:,2); I...

8 days ago | 0

Submitted

Extract linearly independent subset of matrix columns
Loop-free code routine to find a maximal subset of linearly independent columns in a matrix

9 days ago | 6 downloads |

Answered
How do I partition a n by m matrix into equal rows
Hint: Consider repelem https://www.mathworks.com/help/matlab/ref/repelem.html

10 days ago | 0

Answered
Integral calculation using matlab
My difficulty stems from the absolute value which is "outside" of the integral Why is this a difficulty? Because it prevents yo...

10 days ago | 0

Answered
finite difference step size value in fmincon
You might try the sqp or interior point algorithm, instead of whatever fmincon algorithm setting you are currently using. Accord...

10 days ago | 0

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Answered
fmincon output is converging to infeasible point
It appears that you are simply trying to find a point where getCost(Y) returns zero. If so, it might make it easier on the algor...

10 days ago | 0