Matt J

Last seen: Today

6,896 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
Sub-matrix Access in a Square Pattern
Using mat2tiles from https://www.mathworks.com/matlabcentral/fileexchange/35085-mat2tiles-divide-array-into-equal-sized-sub-arr...

19 hours ago | 0

Answered
Add for each element of a matrix the column vector in another dimension
Hi!i have a matrix 136*136. Call this A. This value is the index of a column of another matrix(24*391) Call this B. Then, re...

19 hours ago | 1

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Answered
a 6x6 matrix with unkown x
See eig().

22 hours ago | 0

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local optimisation deterministic optimisation
fvalue = 50 is clearly a better (i.e. lower) objective value than 212.5, so there is every reason to believe that x1=42.5 x2=5...

1 day ago | 0

Answered
Failure in initial objective function evaluation. FMINUNC cannot continue. Need some help
You have set SpecifyObjectiveGradient=true, but your objective function code does not provide a second output for your gradient ...

1 day ago | 2

Answered
Does Matlab have an off-the-shelf function to generate a 2D circular convolution matrix?
You can use func2mat from https://www.mathworks.com/matlabcentral/fileexchange/44669-func2mat-convert-linear-function-to-matrix...

1 day ago | 0

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Do numerical solutions depend on lower and upper bounds even when those bounds are not binded?
Changing the bounds affects where the algorithm can search, which can change the sequence of iterations, which can change which ...

1 day ago | 1

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Answered
What is considered good practice for coding up a function's derivatives, e.g. its Jacobian and Hessian matrices?
However, I imagine it's not best practice to continue doing this, especially when I start considering many more variables, and t...

2 days ago | 1

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Answered
How to compute cost function for fmincon?
r=[0.22 9.94 0.08; 0.16 0.95 0.08; 0.07 0.87 0.08]; R = [0.49; 0.42; 0.19]; omega=0.1; gamma=150; fun=@(x) norm( ...

2 days ago | 1

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Answered
Dividing 3D image to 3D patches
Using mat2tiles, https://www.mathworks.com/matlabcentral/fileexchange/35085-mat2tiles-divide-array-into-equal-sized-sub-arrays ...

3 days ago | 0

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Answered
How to apply Loop Function to this example
x=x0; for i=1:10 x=M*x; end

4 days ago | 0

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Answered
Question on GPU Computing
Make sure you have updated drivers and make sure you restart your computer after their installation. Then use gpuDevice() to sel...

4 days ago | 0

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How to find the length of a curve from a list of points using different length scales?
curveLength = sum(vecnorm( diff( [x(:),y(:)] ) ,2,2))

4 days ago | 0

Answered
Creating matrix with other matrix
[a(:,2:3),b(:),c]

4 days ago | 0

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Answered
abcd is efghijk?
function C= circulant(x) n=length(x); C=zeros(n,n); C(1,:)=x; for i=2:n C(i, :)=[C(i-1, n) C(i-1,...

5 days ago | 1

Answered
parfor problem (broadcast variable)
There's never any gaurantee parfor will be faster, but I would modify the code as follows, B_Data=A_Data(:,2:5)/(0.6*2); B_ref...

5 days ago | 0

Answered
Use inpolygon command for multiple polygon areas
Use discretize(), https://www.mathworks.com/help/matlab/ref/double.discretize.html Apply it separately to all of your xv's and...

5 days ago | 0

Answered
For loop and array type
Best guess - your loop has reached a z for which allcsvfiles{z,1}(:,4) contains text. Use dbstop() to check.

5 days ago | 0

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Array of Structures (not structure array)
I don't know if this is something you explored in (2), but if so, I don't see why it wouldn't cover what you are trying to do. ...

6 days ago | 0

Answered
Memory cost of multiplying sparse matrices
Here's another customized multiplication routine for tall A. I do not know how it compares to Bruno's in terms of speed, but it ...

8 days ago | 0

Answered
Memory cost of multiplying sparse matrices
I believe it is simply because Matlab sparse matrix routines don't handle very tall & thin matrix dimensions very well. It beco...

9 days ago | 0

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Question

Convert a string array to a cell array of strings
Starting with a cell array of strings, >> C={'person','woman','man','camera','TV'}; I know that it is possible to convert to ...

9 days ago | 1 answer | 0

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Answered
Splitting a binary image into 2 parts
There is a small break in the curve which I assumed was supposed to indicate the desired dividing point between the right and le...

9 days ago | 0

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Answered
Plotting 3D network of points and their error ellipsoids
You can use scatter3() to plot the points and ellipsoid() to overlay ellipsoids around them. https://www.mathworks.com/help/mat...

9 days ago | 0

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Answered
fminsearch for existing simulation
As Walter said, fminsearch does not know or care how many lines of code are used to implement your objective function. Bear in m...

9 days ago | 0

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How to set 2 constrain bounds at the same time?
lb=[-10,-30]; ub=[+10,+30];

9 days ago | 0

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Answered
Is convhulln function work for N dimensional
The points you are inputting to convhulln do not form a solid shape in R^5. To within numerical precision, they all lie on a lin...

9 days ago | 0

Answered
Sum each page of a 3D matrix and append sums as rows of new 2D matrix
D=permute(sum(C,1),[3,2,1])

10 days ago | 1

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Answered
Intlinprog function - problem
The optimal solution of a linear program can be discontinuous as a function of the problem data, particular when you have intege...

10 days ago | 1

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Answered
matrix manipulation and transposing
Because when v is a column vector and theta is a row vector, you get implicit expansion, https://blogs.mathworks.com/loren/2016...

10 days ago | 0