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Matt J


Last seen: Today Active since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
5x5 matrix (P) with all 25 values unknown. I have two known matrices of size 5x5 each (A1 and A2) and the relation P*A1*inv(P)=A2. How do I obtain P?
Rewrite the equaion as P(A2-A1)=0 which is equivalent to kron((A2-A1).',eye(5))*P(:)=0. This can be solved with null(). d=lengt...

24 minutos ago | 0

Answered
About Adding Lines to Your startup.m file
A startup.m file needs to be created by you. It can go anywhere in your permanent Matlab path. By permanent, I mean folders that...

37 minutos ago | 0

Answered
How to judge the relatively stable section in the curve
One possibility might be to look at the local span seminorm (max-min) over a sliding window. window=50; lookahead = movmax(cu...

alrededor de 18 horas ago | 0

Answered
Is it possible to reconstruct an image from the number of pixel counts and bins information?
As Walter has shown, it is not an invertible mapping, however, if you use histcounts() instead, there is enough information for ...

1 día ago | 1

Answered
how to find total combination of 5 elements in composition?
Here's an old routine from John D'Errico. I can't find it on the File Exchange anymore, for some reason. combinations=diophanti...

1 día ago | 0

| accepted

Answered
How to remove rows in a nested for loop?
It should start with the column (and therefore the Detected_center point) with the overall shortest distance to a Original_cent...

1 día ago | 0

Answered
Efficient matrix multiplication with weights
A more memory efficient solution is as follows. It has a loop, but is still highly vectorized. Wt=W.'; At=A.'; T=toeplitz(1:N...

2 días ago | 0

| accepted

Answered
Is applying a binary operator (+,-,*,/) to char arrays supported by MATLAB or just a "trick"
I can't find the documentation, but binary operators in Matlab can't define themselves. It had to be deliberate. Also, the char...

2 días ago | 0

Answered
Efficient matrix multiplication with weights
Using sepblockfun() from, https://www.mathworks.com/matlabcentral/fileexchange/48089-separable-block-wise-operations T=toepli...

2 días ago | 0

Answered
Losing pixels with imrotate
So my question was: is there any other way to rotate the images without losing pixels? If you use 'linear' or 'cubic' interpol...

2 días ago | 0

| accepted

Answered
Calculate average between min and max numbers in column 3 depending on values in column 2, for each value in column 1
A=yourMatrix; idx=A(:,1)==7; B=A(idx,:); [~,idx]=maxk(B(:,2),5); C=B(idx,3); result=0.5*(max(C)+min(C))

2 días ago | 1

| accepted

Answered
Iteratively fill structure with custom class objects
I'm puzzled as to why your custom_class() constructor requires the same input argument twice, but this is how I'd do it. rows =...

2 días ago | 0

Answered
What's the inverse of squeeze?
A=reshape(A,128,1,514)

2 días ago | 0

| accepted

Answered
Count the number of times a value repeats between certain rows in a matrix.
A=[2,5,15,65,102; 2,65,1,105,55; 65,104,15,19,5]; skip=1; A1=A(1:end-skip,:); A2=A(skip+1:end,:); M=size(...

3 días ago | 0

| accepted

Answered
How to write an optimization constraint related to neighbors of a node in a graph
You can get the graph adjacency matrix A from the adjacency() command, https://www.mathworks.com/help/matlab/ref/graph.adjacenc...

3 días ago | 0

| accepted

Answered
Complex non-linear least squares fitting of impedance data
Because your model function is linear with respect to x(1) and 1/x(2), it would be beneficial to download fminspleas, https://w...

3 días ago | 0

Answered
random matrix with a minimum number difference for adjacent numbers accepted
Why not as follows? min_diff=0.1; R=rand(1,6); R=R./min(abs(diff(R)))*min_diff; abs(diff(R))

3 días ago | 0

Answered
I need to change the frequency domain of a DFT
stem(2*pi*f,abs(shx),'r')

3 días ago | 1

| accepted

Answered
Read sparse matrix from notepad
S=spconvert(load('S_sp.txt'))

3 días ago | 0

| accepted

Answered
Count number of rows in a matrix based on frequency of one element and value of another element
nnz( matrix(:,1) == 10 & matrix(:,2) > 5 );

5 días ago | 0

| accepted

Answered
How to improve calculation time for a huge matrix?
When speed matters, avoid symbolic math. Also, download https://www.mathworks.com/matlabcentral/fileexchange/74956-ndgridvecs ...

5 días ago | 0

Answered
How to remove rows in a nested for loop?
For Euclidean distance, discard=any( pdist2(Original_center,Detected_center)<Threshold ,2); Original_center(discard,:)=[];...

5 días ago | 0

Answered
Creating a inclined plane with an adjustable dome pattern cutout of it.
You can rotate and replicate the single dome using hgtransform, similar to this example, https://www.mathworks.com/help/matlab/...

5 días ago | 0

Question


Height of a figure spontaneously changes.
When I run the following code, I find that the OuterPosition properties of both figures report the same height and width, as exp...

5 días ago | 2 answers | 0

2

answers

Answered
Coloring axis with gradients?
Do you mean colorbar()?

6 días ago | 0

Answered
Integral of the product of integrals
I=@(y,f) integral( @(x)f(x,y), a, b); I123=@(y) I(y,f1) .* I(y,f2) .* I(y,f3); integral(I123, c, d)

6 días ago | 0

| accepted

Answered
How can I find the distance between adjacent blobs in a segmented image?
Here's one way. mask=imclose(mask, strel('disk',12) ); imshow(mask) blobProps = regionprops( mask , 'Centroid'); blob...

6 días ago | 0

Answered
Solving Equaiton with multplying power
LHS=[0 0 1; -1 0 0; 1 1 -3]; RHS=[0;1;-3]; XYZ=LHS\RHS

7 días ago | 1

Answered
How to only extract part of the folder name?
str='Run 12-27-56.Adaptive PIV.6uqqm6yu' d2=digitsPattern(2); extract(str,d2+"-"+d2+"-"+d2)

7 días ago | 1

| accepted

Answered
How do you reset a persistent variable?
dpb 's answer resolved it..

8 días ago | 0

| accepted

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