Community Profile

# Matt J

##### Last seen: Today
6,532 total contributions since 2009

Professional Interests: medical image processing, optimization algorithms

PLEASE NOTE: I do not read email sent through my author page. Please post questions about FEX submissions in their respective Comments section.

#### Matt J's Badges

View details...

Contributions in
View by

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-' )

19 hours ago | 0

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...

20 hours ago | 0

| accepted

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...

2 days ago | 0

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

2 days ago | 1

| accepted

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

2 days ago | 0

| accepted

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)); ...

5 days ago | 0

| accepted

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 days ago | 0

Submitted

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

6 days ago | 50 downloads |

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...

6 days ago | 0

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 days ago | 0

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 days ago | 2

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 days ago | 0

| accepted

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

9 days ago | 1

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

11 days ago | 0

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);

11 days ago | 0

| accepted

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

12 days ago | 0

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 days ago | 1

| accepted

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 days ago | 1

| accepted

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...

12 days ago | 0

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...

13 days ago | 0

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 days ago | 0

| accepted

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 days ago | 0

| accepted

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 days ago | 0

| accepted

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

15 days ago | 0

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 days 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...

16 days ago | 1 answer | 0

### 1

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

18 days ago | 1

| accepted

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 days ago | 1