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Matt J


Last seen: Today
6 532 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
Approximate a log curve as linear to predict a value
idx=(P<=0.1); c=polyfit(log10(P(idx)),Q_p_1(idx),1); semilogx(P, Q_p_1, P,polyval(c,log10(P)),'x-' )

1 jour ago | 0

Answered
3D Array Rastering
I'm not sure from your description how this should generalize for different N, but perhaps this is what you want: >> N=2; Array...

1 jour ago | 0

| accepted

Answered
Using fminsearch I want to plot the model function whose parameters I'm fitting at each iteration without the figure window stealing focus. How do I do this?
Stop invoking whatever command it is (figure(), axes() ?) that you are using to bring the figure into focus. Calling the plot co...

3 jours ago | 0

Answered
Updating for loop boundaries in MATLAB
for i = 1:size(A,1)

3 jours ago | 1

| accepted

Answered
Calculation of the gradient of a function in BFGS Quasi-Newton Algorithm
With respect to all the variables that are unknown.

3 jours ago | 0

| accepted

Answered
matrix dimensions must agree error
Possibly a missing comma here, K=1/h^2*(2.*diag(ones(1,N+1))-diag(ones(1,N)-1)-diag(ones(1,N),1)); ...

6 jours ago | 0

| accepted

Answered
Define a variable without assigning a value
Perhaps you are trying to do symbolic computations, https://www.mathworks.com/help/symbolic/performing-symbolic-computations.ht...

6 jours ago | 0

Submitted


N-dimensional sparse arrays
Creates an N-dimensional sparse array object, for arbitrary N.

6 jours ago | 50 downloads |

Answered
How can I use 'Least Squares Solver and Jacobian' instead of 'fminunc'?
Assuming D_d is the Jacobian of myfun, it would be, while (sum(abs(beta_u-beta_d))>0.1 && counter< 500) initial_gues...

7 jours ago | 0

Answered
How to view centers on a 3D image
One suggestion is to use this FEX file to display the 3D volume with high transparency https://www.mathworks.com/matlabcentral/...

8 jours ago | 0

Answered
Comparing the performance of colon, loop, and cell indexing
I checked that it is indeed the case with the Run & Time feature. I don't know what that is, but the better test in any case i...

9 jours ago | 2

Answered
Using 'fminunc', I receive Optimization completed because the size of the gradient is less than the value of the optimality tolerance.
If the problem doesn't have a solution satisfying the tolerance condition in your while loop (sum(abs(beta_u-beta_d))<0.1) the...

9 jours ago | 0

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Answered
Join table with different lengths
innerjoin(Grouped_Weight_position{i},Country)

9 jours ago | 1

Answered
Replace array elements with another small array using indexing
b=strrep( strrep(a,[1 4 1],3) ,[3 4 1],2)

12 jours ago | 0

Answered
Split values in an cell array by using a threshold
One way, A_lower = cellfun(@(x) x(x<threshold), A, 'uni',0); A_upper = cellfun(@(x) x(x>threshold), A, 'uni',0);

12 jours ago | 0

| accepted

Answered
How to solve this equation z = c sqrt(x) ?
c=z/sqrt(x)

12 jours ago | 0

Answered
Too many output argument error while using nested functions?
The code you've posted does not make it clear what problem you are encountering. There doesn't appear to be anything wrong in th...

12 jours ago | 1

| accepted

Answered
How to multiply a scalar with matrix within loop and for each iteration store the values in new matrix?
There is no need for a loop: C=A.*reshape(b.^(0:n-1),1,1,[]);

12 jours ago | 1

| accepted

Answered
Function lsqnonlin() has no optimization effect
And I have another question. My code has no optimization effect In this case, your initial guess already is optimal. You can se...

13 jours ago | 0

Answered
Linear Extrapolation with interp2
The only remedy I can think of is to pre-pad the edges of the data V with linearly extrapolated values at distant X, Y. That way...

14 jours ago | 0

Answered
overlaps() with only two polyshap objects
Use the two-argument form, Obstacles=[obstacle3 obstacle2]; criterion = sum( overlaps(car,Obstacles) ) == 1 ; %true if one a...

14 jours ago | 0

| accepted

Answered
Constraints on meshgrid. Remove points outside function
Just apply logical indexing on the appropriate region and set it to NaN, bad=(y<s11(s2)) | (y>s12(s2)); z(bad)=nan;

14 jours ago | 0

| accepted

Answered
How to run a curve approximation on a script using a function defined in a file and display the goodness of fit in a command window
You can't use the curve fit tool for a curve defined in an mfile. You can use lsqcurvefit, if you have the optimization toolbox,...

14 jours ago | 0

| accepted

Answered
Parallel Processing with Multipul GPUs - fftn
You can use gpuDevice() to select different GPUs for different calculations. gpuArray commands run asynchronously without blocki...

15 jours ago | 0

Answered
optimization based upon another optimization
You can write anything you want inside the code for your objective function, including other optimization processes. However, fm...

16 jours ago | 0

Question


Finding handles to figure text
I am attempting to use findobj to retrieve text objects in a plot. For some reason, this fails (R2018a,b). In the following exam...

17 jours ago | 1 answer | 0

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answer

Answered
fmincon nonlinear equality constraint
wopt = fmincon(NegPFMu, w0, [], [], Aeq, beq, lb,[], @(w) mycon(w, Cov, TargetVariance)); function [c, ceq] = mycon(w, Cov, T...

19 jours ago | 1

| accepted

Answered
Uniformly distributed points generation inside quadrilateral with given points
I haven't used it, but this FEX tool claims to be able to do it: https://www.mathworks.com/matlabcentral/fileexchange/71398-ran...

19 jours ago | 1

Answered
Fit a vector to matrix distribution
Can I just plug my new matrix into this and expect a distribution of values out for f1 and D1? I assume you already tried this ...

19 jours ago | 0

Answered
Extract and show non zero pixels of a 2D image in MATLAB
The question seems very open ended. Perhaps as follows, spy(ima)

20 jours ago | 0

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