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Matt J


Last seen: Today
6.918 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
Indexing matrix with index pairs without using linear indexing
Bruno Luong has a fast MEX for this, https://www.mathworks.com/matlabcentral/fileexchange/23488-sparse-sub-access

etwa 3 Stunden ago | 1

Answered
Rotation of 4 vetices
I want to rotate this square toward identified vector of direction n=[a b c] Meaning that [a,b,c] is the desired axis of rotati...

etwa 4 Stunden ago | 0

Answered
How to detect local minima and local maxima in binary image?
Perhaps as follows, A=imread( 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/368827/image.png'); A=imfill(A...

etwa 6 Stunden ago | 0

Answered
answer to a quadratic function
For example, >> roots([1,5,2]) %roots of x^2+5*x+2 ans = -4.5616 -0.4384

etwa 6 Stunden ago | 0

Answered
How to interpolate across 2D Matrix with 3 known parameters?
I am just confused on how I would do this across the different configuration or if its even possible? You interpolate between ...

etwa 21 Stunden ago | 1

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Answered
How can I write summationn constraints for an optimization problem?
fmincon is not the best tool to use for a linear program. In the problem-based framework, you can set up the problem to be solve...

ein Tag ago | 0

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Answered
Using scatteredinterpolant instead of griidedinterpolant
It looks like the latitude and longitude data in your CSV files are already meshgridded. By meshgridding them an additional time...

3 Tage ago | 0

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Answered
Using scatteredinterpolant instead of griidedinterpolant
But when I created a meshgrid with the source data lat-lon points. You should not create a meshgrid, since it consumes unnecess...

3 Tage ago | 0

Answered
"Z must be a matrix, not a scalar or vector." PLEASE HELP!
You should have something like this: x1 = 1:.1:4; x2 = 1:.1:4; mesh(x1,x2, ps2func(x1,x2) ); grid on hold on functio...

3 Tage ago | 1

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Answered
The the interpolate on the spherical coordinate system
I want to make a structure(eg: r=cos^10(theta)) in the spherical coordinate system and plot the combination of (orginal pattern+...

4 Tage ago | 0

Answered
Index in position _ exceeds array bound when executing function, but not when running interactively
What's going on is size(draws,5)=1. You have passed in data whose dimensions are not what the code expects. This may be connecte...

4 Tage ago | 0

Answered
How to add a plot to the structure array for each element
You can achieve what you want to use with subplot(), but I don't think it would be wise to give each time series its own axis. I...

4 Tage ago | 0

Answered
BW consantred cell boundries
You'll find examples of how to do this kind of thing with alphashape() here, https://www.mathworks.com/help/matlab/ref/alphasha...

4 Tage ago | 0

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Answered
Vectorization or for loop (speedup)
Your vectorized code doesn't resemble at all what your for-looped code is computing. The vectorized implementation of your for-l...

5 Tage ago | 0

Answered
In nested for-loops, how and where should I set the counting index (indices?) correctly, for doing numerical root-finding using fsolve?
Well, first of all, you would not use fsolve when doing a gridded root search. In general, the search could be done like this: ...

5 Tage ago | 1

| accepted

Answered
Caclulate Horizonzal Area Between Two Curves And Minimize This Area (Optimization Problem)
EDIT: If you can accept the minimum squared area difference as a criterion, it has a known analytical solution, which is to take...

5 Tage ago | 0

Answered
how to find the right distance evaluation function of an ellipse
See this related thread, https://www.mathworks.com/matlabcentral/answers/555925-does-anyone-know-how-to-use-the-matlab-to-calcu...

5 Tage ago | 0

Answered
Plot a 2D image in projected coordinate systems.
I do not understand how a 3*10095 matrix is being interpreted as an image. You don't to have any pixel values, as far as I can s...

5 Tage ago | 0

Answered
Configure Matlab to use Python without pyenv
Mario's solution worked!

6 Tage ago | 0

| accepted

Answered
How to perform logical AND on intervals of contiguous locations
Using group1s from https://www.mathworks.com/matlabcentral/fileexchange/78008-group1s >> xg=group1s(x)+1; >> yg=splitapply(@a...

6 Tage ago | 0

Answered
How do you create a matrix of matrices?
Put your 10x10x10 arrays in cells https://www.mathworks.com/help/matlab/cell-arrays.html Example: >> A{3,3}=rand(10,10,10) ...

6 Tage ago | 0

| accepted

Question


Configure Matlab to use Python without pyenv
I am trying to call Python from Matlab R2019a on a Windows 10 PC. I have Python 3.7 installed under Spyder 3, but Matlab cannot ...

6 Tage ago | 1 answer | 1

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answer

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...

8 Tage 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...

8 Tage ago | 1

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

8 Tage ago | 0

Answered
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...

8 Tage 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 ...

8 Tage 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...

8 Tage ago | 0

Answered
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 ...

9 Tage 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...

9 Tage ago | 1

| accepted

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