Matt J

Last seen: Today

8,021 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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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 hour 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.

9 hours ago | 18 downloads |

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/...

10 hours ago | 0

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

14 hours 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; ...

1 day ago | 0

Answered
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')

1 day 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....

1 day 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.';

1 day ago | 0

Answered
I need that the values of x(1) and x(2) are not higher than 1 using the Genetic algorith for optimization
ub=[1,1,inf];

1 day ago | 1

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

1 day 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)

1 day 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 ...

1 day 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...

1 day ago | 1

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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.

2 days ago | 0

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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...

3 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.

3 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...

3 days ago | 1

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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 ...

3 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.

3 days ago | 1

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?

3 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...

4 days ago | 0 answers | 1

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answers

Answered
Is there a way to access array elements returned by a function directly
In theory, it is possible to make a function directly indexable using OOP trickery, https://www.mathworks.com/matlabcentral/fil...

4 days ago | 0

Answered
Fitting cone/cylinder of known dimensions to 3D surface data
If you know where the given surface samples would be located on an unrotated/untranslated version of the cone/cylinder, then the...

4 days ago | 1

Answered
How do I answer this question?
Hint: a:b:c

5 days ago | 0

Answered
Problem with optimization function fcn2optimexpr
It is likely that you meant to do element-wise exponentiation .^ somewhere in your function, but have ^ instead.

5 days ago | 0

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Answered
Shape recognition from user input and obtain XYZ coordinates
I thought it would be a simple use of the bwboundaries function or regionprops() but I can't seem to do so. Assuming the shapes...

5 days ago | 0

Answered
How to divide an image into non-overlapping blocks size 4x4?
You can use sepblockfun https://www.mathworks.com/matlabcentral/fileexchange/48089-separable-block-wise-operations out =sepblo...

5 days ago | 0

Answered
Define a matrix in terms of kronecker product
n=3; e=ones(1,n); A=eye(n); B=kron(e,A); p=reshape(1:n^2,n,[]).'; C=kron(A,B); C=C(p,:)

5 days ago | 0

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Answered
Define a matrix in terms of kronecker product
n=3; I=eye(n); e=ones(1,n); z=zeros(1,n); C=cell(n,1); for i=1:n q=z; q(i)=1; C{i}=kron(kron(I,e),q); end ...

5 days ago | 0

Answered
Fitting cone/cylinder of known dimensions to 3D surface data
I've recently added a cone-fitting routine to this FIle Exchange package, https://www.mathworks.com/matlabcentral/fileexchange/...

6 days ago | 0

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