Matt J
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.
Statistics
RANK
7
of 239.349
REPUTATION
20.177
CONTRIBUTIONS
192 Questions
7.974 Answers
ANSWER ACCEPTANCE
75.52%
VOTES RECEIVED
2.711
RANK
265 of 16.806
REPUTATION
5.116
AVERAGE RATING
4.90
CONTRIBUTIONS
33 Files
DOWNLOADS
289
ALL TIME DOWNLOADS
43158
CONTRIBUTIONS
0 Posts
CONTRIBUTIONS
0 Public Channels
AVERAGE RATING
CONTRIBUTIONS
0 Highlights
AVERAGE NO. OF LIKES
Your submissions were downloaded 250 or more times in a month
Awarded to Matt J on 01 Nov 2019
Publish your first review
Awarded to Matt J on 09 Oct 2019
Your submissions received 25 five star ratings
Awarded to Matt J on 09 Oct 2019
Publish your first submission
Awarded to Matt J on 09 Oct 2019
Answer 50 questions that were unanswered for more than 30 days
Awarded to Matt J on 12 Oct 2017
Contribute at least one answer each month for 36 consecutive months
Awarded to Matt J on 20 Jul 2017
Accept 50 answers given by other contributors
Awarded to Matt J on 20 Jul 2017
100 of your answers have been accepted
Awarded to Matt J on 20 Jul 2017
Provide your first answer ever to someone else's question
Awarded to Matt J on 20 Jul 2017
Content Feed
Finding the vertical offset of a gaussian fit
This File Exchange routine does gaussian+constant fitting: https://www.mathworks.com/matlabcentral/fileexchange/69116-gaussfitn...
etwa 2 Stunden ago | 0
How to set a custom equation to fit 5 points in space by fitsurface?
I can't find "fitsurface" in the Mathworks documentation, but the fit is easy enough to do algebraically. x=x(:); y=y(:); z=z(:...
etwa 9 Stunden ago | 0
Why is x(:) so much slower than reshape(x,N,1) with complex arrays?
The following simple test seems to support @Bruno Luong's conjecture that (:) results in data copying. The data of B1 resulting ...
etwa 13 Stunden ago | 0
Is it possible to correctly perform a multi-dimensional FFT on a 1D linearised version of a 3D array?
Reshaping to and from 3D format should not add significant cost: Nx = 256; Ny = 256; Nz = 128; N = Nx*Ny*Nz; A0 = rand(N,1)...
ein Tag ago | 0
| accepted
Question
Why is x(:) so much slower than reshape(x,N,1) with complex arrays?
The two for loops below differ only in the flattening operation used to obtain A_1D . Why is the run time so much worse with A_3...
ein Tag ago | 3 answers | 1
3
answerssee the 3d image and see the coordinates while moving the mouse over the image
You can use imshow() to display any particular slice of the image and then use the axis datatip button to get the in-slice 2D co...
2 Tage ago | 0
How do i find the coordinates of a boundary
How about simply, [m,n]=size(Image); I=boundary(:,1); J=boundary(:,2); corner1 = [1, max(J(I==1))]; %row/column coordinat...
2 Tage ago | 0
How to Draw an ellipsoid between two 3d coordinates
Another way would be to use the ellipsoidalFit.groundTruth method in this File Exchange submission. https://www.mathworks.com/m...
2 Tage ago | 0
Trying to count the number of pixels in an image over a specific RBG value
results.area=nnz(imstd>90);
2 Tage ago | 0
| accepted
Normally distributed random numbers with fixed sum
Why not simply, x(1:N-1)=randn(1,N-1); x(N)=fixedValue-sum(x(1:N-1))
2 Tage ago | 0
Only analyze what is outlined in black in an image
If you have a binary mask of the circles, you can just do numBlack = nnz( circles & ~BW ); numWhite = nnz( circles & BW);
2 Tage ago | 0
If the quadprog problem is infeasible, how i can solve it with a certain tolerance?
It never really makes sense to have more equality constraints (here 36) than you do unknowns ( here 6). In order for the problem...
4 Tage ago | 0
| accepted
How to construct a "ones" matrix with zero blocks in the diagonal
repelem(1-eye(4),4,4)
5 Tage ago | 1
Iterative solution of non-linear equation with a provided guess value?
You could use fzero's OutputFcn option https://www.mathworks.com/help/optim/ug/fzero.html#btn3z5s-options to access the sequen...
5 Tage ago | 0
Iterative solution of non-linear equation with a provided guess value?
Using fsolve() instead of fzero(), you could solve the problem as a system of two equations in two unknowns. The two unknowns ar...
5 Tage ago | 0
Failure in initial user-supplied nonlinear constraint function evaluation
One problem: nonlcon = @simple_constraint; There is no function called 'simple_constraint' in your attached script. There is a...
5 Tage ago | 1
| accepted
for loop for permutations of for length of array
List=nchoosek([a,b,c],2); for i=1:size(List,1) p1=List(i,1); p2=List(i,2); ... end
6 Tage ago | 1
| accepted
How do I use an if-else structure inside a for loop to investigate if each component of a row vector is inside or outside the boundaries?
Hint: for i=1:numel(vec) v=vec(i); end
7 Tage ago | 0
2*2 Matrix factorization/decomposition
I also found out what I wanted may have something to do with PLU(permuted lower upper decomposition), but am clueless to how to ...
7 Tage ago | 0
How can I call a script within a for loop, looping over multiple files?
result = scriptname(ID{nSubject},Visit{nVisit});
7 Tage ago | 0
| accepted
I am trying to find the exact distance of a curvy line.
Why not as follows? I2 = imread('image.jpeg'); blue=bwareafilt( I2(:,:,1)<=50 & I2(:,:,2)<=50 & I2(:,:,3)>=200, 1); Len...
7 Tage ago | 0
| accepted
Number of branches per branch point
Perhaps as follows: k=ones(3); k(5)=0; neighborCount=conv2(double(BW),k,'same'); neighborCount=neighborCount.*(neighborCo...
7 Tage ago | 0
| accepted
Rank deficient error.
Are you attempting to do matrix division? if not use ./ instead.
7 Tage ago | 1
| accepted
Merge struct with matrix
You cannot avoid a for-loop altogether, but you can avoid writing your own for-loop as follows: tmp=num2cell(modelOutputSignal,...
7 Tage ago | 0
| accepted
Unable to detect Iris boundary using imfind circles
Increasing the lower radius bound as suggested by @Jonas as well as increasing the sensitivity setting seems to help: A=any( im...
8 Tage ago | 0
| accepted
adjusting the code from optimization output from minimum to maximum
fun=str2func(FUNCTION_NAME); fun=@(x) -fun(x); [Scaled_x_Single,fval,exitflag,output,population,scores] = ga(,3,[],[],[],[],...
8 Tage ago | 0
Question
Re-import a binary map into Image Segmenter or Color Thresholder
I have generated a binary mask of an image using the Image Segmenter app. I am wondering if it is possible to re-import that mas...
8 Tage ago | 1 answer | 0
1
answerFind elements from a submatrix in the main 3D matrix
[row,col]=find( reshape( ismember(M(:),A(:)) , size(M) ) );
8 Tage ago | 1
| accepted
How to smooth data to a negative curve
Thie File Exchange submission allows you to do spline smoothing with monotonicity constraints: https://www.mathworks.com/matlab...
8 Tage ago | 0
| accepted
Create new field on struct from names on existing field
names={Stimuli.names}; idxBlue=contains(names,["H1" "H2" "H3"]); idxRed =contains(names,["H4" "H5" "H6"]); [Stimuli(idxBlue...
8 Tage ago | 0
| accepted
