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Matt J


5 709 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
Find argmin of function with unique vector
You need to write code that generates in vectorized form. Then the rest is easy. The correct way to code your original example ...

environ 5 heures ago | 0

Answered
Any way to speed up calculation of a large complex exponential?
One reason exp(A) is signficantly faster is that it is always Inf for the values of A you are feeding in. There is no computatio...

environ 23 heures ago | 1

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Answered
How to accelerate multiple Backslash Operations?
If you have the Parallel Computing Toolbox, this is readily done on the GPU C=pagefun(@mldivide,gpuArray(A), gpuArray(b));

environ 23 heures ago | 0

Answered
indexing diagonals out of a 4d matrix
[M1,N1,M2,N2]=size(g); M=min(M1,M2); N=min(N1,N2); f=diag(reshape(g(1:M,1:N,1:M,1:N),M*N,[])); f=reshape(f,M,N);

environ 23 heures ago | 0

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Answered
Derivative of Function handle (To obtain the derivative of constraints in function fmincon)
You can use the Symbolic Math Toolbox to obtain the expression for the derivative, and then use matlabFunction() to convert from...

1 jour ago | 0

Answered
How to speed up large marix multiply?
If you download mtimesx, you can avoid an explicit transpose, mtimesx SPEED B=mtimesx(A,A,'c');

1 jour ago | 0

Answered
obtain the fourier trasnform doing the fft. Do I need to normalize??
To approximate a continuous Fourier transform integral, you need to multiply by the time step, tkef1= fft(tket(:,34:34),L) * Ti...

1 jour ago | 1

Answered
Where is the difference between these two lines?
My guess is that you have called the isfolder command with two different versions of the input, but with hidden characters or ac...

1 jour ago | 0

Answered
How can I edit a camera calibration .mat file?
If you already plan to use approximate parameters, why not just create a stereoParameters object directly? https://www.mathwork...

1 jour ago | 0

Answered
Problem extracting data in a for loop
Your code is calling a function called Objectdetection, whereas the function you've posted and presumably intend to call is name...

1 jour ago | 0

Answered
How to assign corresponding lat , Lon to grid points
You should just leave the grid data in its original form, without any of the NaN-removal or reshaping. None of the changes seem ...

1 jour ago | 0

Answered
How to assign obeject properties to another object
As long as the properties are not Dependent, you can use the attached routine to assist with the property-copying in the subclas...

1 jour ago | 0

Answered
logical expression in objective function
The way you would do this is to introduce additional binary variables, b1=optimvar('boolean1','Type','integer','LowerBound',0,'...

2 jours ago | 1

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Answered
Quadratic programming for GPU computing
You are free to use gpuArray variables within your objective function, and in constraint functions in the case of fmincon. Unfo...

2 jours ago | 0

Answered
curve-fitting problem: Unrecognized option name 'showstatus' in OPTIMSET ?
Not much more informative, unfortunately... But now that you've trapped the error with dbstop you can dbup and dbdown through t...

4 jours ago | 0

Answered
Locate rectangles in an image and segment
This seems to emphasize the vertical lines well enough. houghlines shouldn't have too much difficulty with this, load image ...

4 jours ago | 1

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Answered
How would I plot conic sections in a 3D cone and extract certain parts of the graph?
The easiest would be to have the plane fixed as the xy-plane and just rotate/translate the cone around in 3D space to get differ...

4 jours ago | 3

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Answered
What frustrates you about MATLAB?
blkdiag does not return the result in sparse form, or provide an option to do so. I am puzzled that this wasn't an obvious use c...

4 jours ago | 0

Answered
Make curve fitting faster
I want to in each voxel fit this 10 points by specific biexponencial curve (so I receive parametric maps of brain) @Marek, D...

4 jours ago | 0

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Answered
How to speed up or parallelise multiple calls to lsqcurvefit
This thread may help, https://www.mathworks.com/matlabcentral/answers/431697-make-curve-fitting-faster

4 jours ago | 0

Answered
how to find an empty row in a table
loc=cellfun('isempty', yourTable{:,'column1'} ); yourTable(loc,:)=[]

4 jours ago | 0

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Answered
How to fast create a specific matrix
hankel(zeros(1,4),0:3)

5 jours ago | 1

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Answered
"Undefined function 'mtimes' for input arguments of type 'function_handle' " error comes up
Keep everything sym, syms x y q %<--- u1=(x/(x+y)); u2=(y/(x+y)); g12= 0.218+0.276/(1+0.622*q); %<--- dg1=subs( di...

5 jours ago | 0

Answered
Averaging and Storing Stacked Cell Array With 'NaN' Values
Averages = mean( cat(3,nitrogenCell{:}) ,3,'omitnan');

5 jours ago | 1

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Answered
Error using && in if conditional statements
I believe your entire code can be replaced with 3 lines, [x,y,z]=ndgrid(0:N); fh=( c/2 ) * ( sqrt((x(:)/lx)^2 + (y(:)/ly)^2 ...

5 jours ago | 0

Answered
Reference to non-existent field 'output' Error
I don't see where you've created handles.output. So, no wonder Matlab complains that it can't find it.

5 jours ago | 1

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Answered
Removing Rows from Character Vector?
Works fine for me, Materials=["Iron";"Steel";"Wood";"Cheese"]; DF=logical([1 0 0 1].'); >> MaterialsFinal = Materials(DF) ...

5 jours ago | 0

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Answered
Change in Intrinsic Parameters
Auto-focus seems like a highly probably explanation. If the focal length is physically changing, then the calibration code is d...

5 jours ago | 0

Answered
Why does skeletonization sometimes reduce horizontal rectangles to single pixels?
It is because the lower rectangles have an even number of rows, so their "center line" in continuous space does not coincide wi...

5 jours ago | 0

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Answered
What should I do if Fsolve can not find a solution in the middle of the solution ?
Look what it says: Equation solved! Isn't that great?

6 jours ago | 2

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