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Matt J


Last seen: Today
6,316 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.

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Answered
Is there a way to create a symmetric Toeplitz matrix and bounding its eigenvalues?
R=fft(eye(400))/sqrt(400); e=zeros(1,400); e(2)=-10; e(end-1)=+10; e=ifftshift(e); T=(R'*diag(e)*R); T=real((T+T.')/2);...

12 hours ago | 1

| accepted

Answered
optimization problem wont find any solutions
The problem is infeasible, or your initial guess x0 is too far from a feasible point.

18 hours ago | 0

Answered
making coarse matrix from fine resolution matrix
A 3rd approach, more memory conserving and, I believe, faster than the currently Accepted answer. Z1=randi(100,8640,4320); u...

1 day ago | 1

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Answered
3D image template matching by using (normalized) cross correlation?
I've never used it myself , but you could try this FEX submission, https://www.mathworks.com/matlabcentral/fileexchange/73946-n...

1 day ago | 0

Answered
making coarse matrix from fine resolution matrix
If you have the Image Processing Toolbox, abc1=imresize(Z1,[3600,1800])

2 days ago | 1

Answered
find the element in matrix of intersecting vectors
attainedA=( max(a,[],1)==a ); attainedB=( max(b,[],2)==b ); result = c(attainedA & attainedB)

2 days ago | 1

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Answered
Quadprog message: The problem is non-convex
You cannot submit a problem that is borderline convex to quadprog if it is using an algorithm that expects convexity. If you do,...

2 days ago | 0

Answered
How to define a plane by matrices instead of a function?
For example, A = [104,122,111]; B = [253,122,153]; C = [104,124,111]; normal=normalize( cross(A-B,A-C),'norm'); %calcul...

3 days ago | 1

| accepted

Answered
When using the cftool, should I use Trust Region or Levenberg-Marquardt?
You can read here about the relative limitations of the 2 algorithms, https://www.mathworks.com/help/optim/ug/lsqcurvefit.html#...

3 days ago | 0

| accepted

Answered
Need Math to Rotate XYZ Point Around A-B Rotary Axes
See Rodrigues' formula, https://en.wikipedia.org/wiki/Rodrigues%27_rotation_formula Also, though you are apparently not worki...

3 days ago | 0

Answered
How to run fmincon using following function?
With no constraints, it would simply be, x=ones(200)/(-c*B);

3 days ago | 0

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Answered
No solution found when solving 3 non linear equations
A numerical sweep also gives evidence that there is no solution [x1,x2,x3]=ndgrid(linspace(-pi,+pi,512)); F1=cos(-x1+x2)+c...

4 days ago | 0

Answered
How do you call an inline or anonymous function within cellfun?
I reverted back to the for loop This might be faster than the for-loop, allB=[B{:}]; idx=ismember(allB,A); Blens=cellfun('l...

4 days ago | 1

Answered
How do you call an inline or anonymous function within cellfun?
But would still like to know how to use anonymous functions within cellfun There's no difference. Since findVal is already a fu...

4 days ago | 0

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Answered
Converged to an infeasible point.
The initial guess you have chosen x0 = [1,1,1,1,1,1,1,1]; seems very arbitrary. You should devise an initial guess more likely...

5 days ago | 0

| accepted

Answered
Matrix sequence manipulation for multiple value assignment
e=1:numel(A); lidx= any(idxes(:,1)<=e & e<=idxes(:,2),1); A(lidx)=1;

5 days ago | 0

Answered
Matrix sequence manipulation for multiple value assignment
If the intervals will always be disjoint, A=zeros(20,1); n=numel(A); A(idxes(:,1))=1; A(idxes(:,2)+1)=-1; A=cumsum(A(1:n)...

5 days ago | 0

Answered
Getting the coordinates of vertices of an A4 sheet with coins on it, for its further projective transformation and coin detection
The Computer Vision Toolbox has a few corner point detector apps, https://www.mathworks.com/help/vision/ug/point-feature-types....

6 days ago | 0

Answered
Relocate a value of a vector.
A=[1 2 3 4 5 6 7 8 9 0]; i=2; %position removed j=7; %target position B=A; k=i<j; B(i)=inf; C = [B(1:j+k-1),A(i),...

8 days ago | 2

| accepted

Answered
table less than operator
Are you sure you do not instead want to compare the content of a variable in the table to something?... yes this what I'm trying...

8 days ago | 0

Answered
Why is N not being displayed?
Because the loop condition is never satisfied and therefore nothing within it is ever executed. I think you meant to have, whil...

8 days ago | 0

| accepted

Answered
Displaying information about the data set by clicking on its plot and then show a value that is associated with the (x,y) point
.... set(dcm,'UpdateFcn',@(t,e) myupdatefcn(t,e,x,y) ); function txt = myupdatefcn(~,event,xdata,ydata) pos = get(eve...

8 days ago | 0

| accepted

Answered
Getting the linear portion of a non-linear curve
I'm not sure why a 2nd derivative test wouldn't have worked, as long as your points are noiseless: i=find( abs(diff(x,2))>somet...

8 days ago | 1

Answered
How to return the smallest vector.
If you "have them" in cell array form, then you could do something like this: >> vectors={[3 4 5],[1,2],[5 6 7 8]} vectors =...

8 days ago | 0

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Answered
a problem with setting fmincon options?
I would guess that you entered your options object as the 9th input argument to fmincon when it really should be the 10th. If yo...

9 days ago | 0

| accepted

Answered
set Precision in lsqcurvefit
You cannot do such a thing with lsqcurvefit. What you describe would require that you rewrite your objective function and bounds...

9 days ago | 2

Answered
Delete part of an image
[m,n]=size(oldImage); x=(1:n); y=(1:m).'; mask = (x-innerCenterX).^2+(y-innerCenterY).^2>=innerRadius^2 & ... (x...

9 days ago | 2

| accepted

Answered
Find the orientation of the skeletonized image
You can use houghlines to get the endpoints of all the line segments in the image. From that, you can easily calculate their slo...

9 days ago | 0

Answered
Using cell array to define Argument list in function Handle
That is not the right approach. You should be taking advantage of the fact that this is Matlab, and that your variables are allo...

10 days ago | 0

Answered
Divide plane into two separate planes
Let b1 and b2 be basis vectors for the plane and let x0 be a point in the plane. Then, for example, x0(:) + b1(:)*randn(1,N) + ...

10 days ago | 0

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