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Matt J


Last seen: Today
6 734 total contributions since 2009

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
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...

ungefär 2 timmar ago | 0

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...

ungefär 6 timmar ago | 0

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

ungefär 8 timmar ago | 0

Answered
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...

en dag 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); ...

en dag ago | 0

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...

en dag 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...

en dag 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...

2 dagar ago | 1

| accepted

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...

2 dagar ago | 1

| accepted

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

2 dagar 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...

2 dagar 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

3 dagar ago | 4 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

4 dagar 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...

4 dagar 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...

5 dagar ago | 0

| accepted

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...

5 dagar ago | 0

Answered
Algorithm to extract linearly dependent columns in a matrix
See this FEX contribution https://www.mathworks.com/matlabcentral/fileexchange/77437-extract-linearly-independent-subset-of-mat...

5 dagar ago | 2

Answered
fminbnd loop leads to same optimizer
In addition to hwat John said, you could plot the function to confirm whether fminbnd is giving you a good approximation of the ...

5 dagar ago | 0

| accepted

Answered
return a single vector after a for loop and not individual results
For a fully vectorized solution: [maxval,place]=max(Divergence<=5,[],2); place(maxval==0)=nan; Or, to do the same with a loop...

6 dagar ago | 0

| accepted

Answered
Index in position 1 exceeds array bounds (must not exceed 1). FMINCON
Make theta0 a column vector: >> theta0 = [2,0.2,0.1,0.4].' theta0 = 2.0000 0.2000 0.1000 0.4000

6 dagar ago | 0

| accepted

Answered
How can I determine the amount of times a certain value can be achieved by summing values in a matrix?
Below is a more advanced version of my original answer, which is showing greater empirical succes. It incorporates initializatio...

7 dagar ago | 0

Answered
How to logically index multiple indices while indexing other indices normally?
You probably won't notice much difference with such small data sizes, but reshape is slightly better than permute because it wil...

7 dagar ago | 0

| accepted

Answered
How do I get every combination of 3 vectors?
Example: [X,Y,Z]=ndgrid(1:3,10:15,100:102); [X(:),Y(:),Z(:)]

7 dagar ago | 1

Answered
Particularly strange bug using the eval function
I also know that MATHWORKS would prefer me not to define variables that clash with their own builtins. However, the code st...

7 dagar ago | 2

Answered
Can one set up initial values for fminbnd?
No, you cannot. However, you might get a comparable effect if you use fminsearch instead, setting your objective to Inf outside ...

7 dagar ago | 0

| accepted

Answered
Given a point, locate 3 point in different 8 directions.
Or maybe this is what you want. In the code below, A is your image and the result Neighbors(i,j,:) contains all 9 neighbors of A...

7 dagar ago | 0

Answered
calculate mean in a for loop
No need for loops, Mean_answer=cumsum(data,2)./(1:size(data,2));

7 dagar ago | 0

Answered
Given a point, locate 3 point in different 8 directions.
I'm not sure I understand what the how-to challenge is in the question, but the approach that I think you want is to calculate a...

7 dagar ago | 0

Answered
How can I determine the amount of times a certain value can be achieved by summing values in a matrix?
This solution (EDITED) requires the Optimization Toolbox: LengthVal = [50,50 ,60,70]; %User Input N=numel(LengthVal); X...

9 dagar ago | 1

Answered
System of equations: Two different versions of Matlab, with the same script, give different solutions
Seems to me that you are getting the same solutions for each fixed Current level, but presented to you in a different order depe...

9 dagar ago | 1

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