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Matt J


Last seen: Today
8,030 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Question


Shouldn't bwconvhull() be idempotent?
Shouldn't the following two calculations give the same results? load BWimage A=bwconvhull(BW); B=bwconvhull(bwconvhull(BW));...

35 minutes ago | 0 answers | 0

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Answered
circle through 3 points equation
You can use circularFit() from this File Exchange submission https://www.mathworks.com/matlabcentral/fileexchange/87584-object-...

3 hours ago | 0

Answered
How to solve this simple matricial system?
u=A\(h*G)

5 hours ago | 0

| accepted

Answered
Verifying an Vector composition
issorted(A(1:ceil(end/2))) & all(A==flip(A))

5 hours ago | 0

Answered
how do I select only the segmented region from a original image in MATLAB
You could do, S=regionprops(rgb_label,img,'Image')

5 hours ago | 0

Answered
Jacobian of a state matrix over time using jacobianest
I don't think there is anything sub-optimal about the way you're using jacobianest now. In fact, by keeping the loop external to...

10 hours ago | 0

Answered
Draw a gradient circle within a circle
One way might be to use a patch with vertex interpolation, as in this example. https://www.mathworks.com/help/matlab/ref/patch....

1 day ago | 1

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Answered
How to extrapolate a level curve form a 3D plot of a 2-variables function?
Youc an just use contour(). contour(Mach,Alfa,CM_plot,0);

1 day ago | 0

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Answered
Find very small zeros of a polynomial
It would be easier, both numerically and analytically, if you made the change of variables z=-(0.5/r)^6 and find the roots of th...

1 day ago | 0

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Answered
How can I register (merge) two images using homography matrix?
I'd recommend using fitgeotrans() rather than an unnormalized DLT approach. https://www.mathworks.com/help/images/ref/fitgeotra...

1 day ago | 0

Submitted


Object-oriented tools for fitting conics and quadrics
A tool set for fitting various conics and quadric surfaces, e.g., ellipses, cylinders, spheres, planes, cones, and lines.

2 days ago | 18 downloads |

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Answered
How to plot 3d plane of type where one variable is missing like x + y = 0.....
If you mean that you have a plane equation of the form a*x+b*y+0*z=d, then you can use https://www.mathworks.com/matlabcentral/...

2 days ago | 0

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Answered
Array division of two non-zero arrays returns zero
W = double(Y(:))./double(X(:).');

2 days ago | 0

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Answered
parfeval inside a class method does not update a class property
Couldn't you do something like this? function execute(self, N) gd=gpuDevice; ...

3 days ago | 0

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Subset and nanmean of a three dimensional array to a have a 2d array 1xndim
pt_lev8=reshape(pt_lev8,[],348); final = mean(pt_lev8(s1pos,:),1,'omitnan')

3 days ago | 0

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Answered
parfeval inside a class method does not update a class property
You cannot broadcast handle objects to a parpool. They simply get cloned and used as independent class instances on the workers....

3 days ago | 1

Answered
Zero Steps Performed in lsqcurvefit Calculation for Matrix Optimization Problem
Seems like the problem has a simple analytical solution, [A,B]=eig( D\diag(P)/(D.') ); A=A.';

3 days ago | 0

Answered
Image registration and motion correction
Maybe downsample the images to reduce computation and use imregtform() instead of imregister()?

3 days ago | 0

Answered
3D/2D matrix multiplication without using a loop
Assuming S_r will always be square, B=reshape( S_r*A(:,:), size(A)); %B(:,:,k)=S_r*A(:,:,k)

3 days ago | 0

Answered
Constructor for a class, that accepts name-value pairs for setting properties
With a recent Matlab version, you can do, classdef classX properties Prop1, Prop3; end methods ...

3 days ago | 1

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Answered
Fast vector reshaping/permutation
Edit 2 for further context: ...Essentially this is the type of overall operation we are looking to do: This will be more effici...

3 days ago | 1

| accepted

Answered
Failure in initial objective function evaluation. FMINCON cannot continue.
The problem has nothing to do with fmincon. You must first make sure that your objective function runs without errors at x0.

4 days ago | 0

| accepted

Answered
how to ignore multiple clicks on buttun in matlab app designer
You can set the Interruptable property of the button to 'off' and the BusyAction property to 'cancel'. https://www.mathworks.co...

4 days ago | 0

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Answered
Least Trimmed Squares fitting
If you don't have too many unknown parameters to fit, you could implement it easily with fminsearch.

4 days ago | 0

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Answered
Row-wise individual circshift of a 3D-matrix without using a loop
%%% Precomputations - do this block only once [m,n,p]=size(A); [I,J,K]=ndgrid(1:m,1:n,1:p); %%% Jshift=mod(J-RowsShift-1,n...

4 days ago | 1

| accepted

Answered
Can I run multiple instances (say, 2) of matlab independently on the same computer, all using parfor and (ideally) different cores?
Does it make sense to run multiple scripts in different matlab instances? No, that would be a reinvention of what the Parallel ...

5 days ago | 0

Answered
These two sections of codes for getting the mean should give the same answer, but why don't they?
The first two elements differ by a very small amount. Likely just floating point noise.

5 days ago | 1

| accepted

Answered
Fast vector reshaping/permutation
No, permute() will be the fastest way (on the CPU). How does the GPU hurt other areas of your application?

5 days ago | 1

Question


On my Matlab Desktop UI is a minimize/maximize toggle button. I want minimization/maximization to occur only when I press this button.
I have configured my Matlab Desktop UI so that among the sub-panels displayed are the Command Window and the Workspace pane. I h...

5 days ago | 0 answers | 1

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