Community Profile # Matt J

Last seen: Today Active since 2009

Professional Interests: medical image processing, optimization algorithms

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How can I perform large sparse matrix multiplication efficiently when one sparse matrix is block diagonal?
The typical value of K is 50. Since the third dimension is so small, it's probably worthwhile just storing the data as a length...

ungefär 15 timmar ago | 0

How can I perform large sparse matrix multiplication efficiently when one sparse matrix is block diagonal?
With ndSparse, did you try the summl() method? It's more memory intensive, but it can also be faster. Here's what I see in a sim...

en dag ago | 0

Commenting Code inside for loop. Orientation Issue
No, but enhancement requests for this have been submitted (by me at least).

2 dagar ago | 0

Custom class properties and method attributes
I don't know why it's not documented, but apparently there is a Description attribute that can be added, e.g., classdef myclass...

2 dagar ago | 1

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How do I get the indexes of a symmetrical logical matrix without getting repetitions of those indexes?
[I,J]=find(yourMatrix); keep=(J>=I); I=I(keep); J=J(keep);

2 dagar ago | 0

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calling seperate members of a vector function
There's no way to do that. You could do it if the components are held in struct form, e .g., F=@(x,y) struct('a',x-y,'b', y^2);...

3 dagar ago | 0

Matlab does not find new method in class folder without "clear classes"
I don't know if it's intended or not, but my experience is that it only happens when your class is in a @-directory. If you put ...

4 dagar ago | 1

Finding consecutive zeros in an array. Not able to solve using diff command
Using, https://www.mathworks.com/matlabcentral/fileexchange/78008-tools-for-processing-consecutive-repetitions-in-vectors [~,~...

4 dagar ago | 0

Solve equation with multiple values for V
Because there is no analytical solution. Try vpasolve() or fzero() instead.

4 dagar ago | 0

Help. Plot graph calculation
You mean, how to plot the triangle? You can do, x=linspace(0,3,1000); y=(1-abs(x-1)); y=y.*(y>=0); plot(x,y)

4 dagar ago | 0

Intensity Profile of a specific line
You could just use improfile() https://www.mathworks.com/help/images/ref/improfile.html

4 dagar ago | 0

Multiple plots on the same graph
I think the line where you plot is supposed to look like, semilogx(tc,PDF); but the code you've posted contains no variable c...

4 dagar ago | 0

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How to create a custom Matrix following a set of parameters
n=5; A=-diff(eye(n+2),2,1); A(:,1)=[]

4 dagar ago | 0

How to create a custom Matrix following a set of parameters
n=5; c=[2,-1,zeros(1,n-2)]; r=[c,0]; A=toeplitz(c,r)

4 dagar ago | 0

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How to covert a 1D vector to 2D matrix with overlapping effectively?
X=randi(30, 1,14); segment_size = 4; overlap_rate = 0.5; d=segment_size*overlap_rate; idx=(1:segment_size)'+ ( 0:d:(num...

5 dagar ago | 0

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Plot elements of specific size
You could probably use a listener to increase the MarkerSize etc as a response to zooming in or out. The code below is an imple...

5 dagar ago | 1

Plot elements of specific size
First, I don't care about interactive zooming. I'd like to save a pdf. If the zooming is happening only after the pdf conversio...

5 dagar ago | 0

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how to write a function which converts graphs from linear scale to logarithmic scale and plot them both?
To convert the scale of an existing graph from linear to log, you can do, set(gca,'YScale','log') set(gca,'XScale','log')

5 dagar ago | 0

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Cropping the same roipoly for multiple images
I don't understand what you mean by "cropping" an image to a non-rectangular region. An image, cropped or otherwise, is an inher...

5 dagar ago | 0

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Calculating value of function in point
f=@(x)2*x+2.^x; test = evaluate(f,0,6,7) function matrix = evaluate(f,x,y,n) a = linspace(x,y,n); b = f(a); matrix = [a;b...

5 dagar ago | 0

Failure in initial objective function evaluation. FSOLVE cannot continue.
Is there supposed to be a '+' after teta1s? fval(2,1)=beta1c+teta1s+((2.66*mumr...

5 dagar ago | 0

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How to write a function with logical condition which takes an array and turns back an array?
K=sinc(alpha/pi*(x-y.'));

5 dagar ago | 1

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2D matrix multiply with 3D array
[m,n,p]=size(B); Br=reshape(B,[],p); Br=Br(:,1:200); %might not be necessary U1=Br*u; V1=Br*v; c=reshape( sum(U1.*V...

5 dagar ago | 0

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using eig to find the eigenvalues and eigenvectors of a large matrix on GPU
It might be a question of your hardware. On the GTX 1050 in R2020b, I see only about a 10% speed-up in double precision and abou...

5 dagar ago | 0

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A function does not work with an array as an input argument
args={'ArrayValued',1}; MyFun = @(a, x) ( integral(@(k) k .* (1 ./ ( 1 + (a*k - x).^2 )), -1, 1,args{:}) ./ ... integral(@(k...

6 dagar ago | 1

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There's nothing wrong with post-rounding, however setting lb(i)=ub(i)=0 for the appropriate variables should force them to an ex...

6 dagar ago | 0

Connect the optimizer function to data extracted from another software
You've written a fitness function f=@(~) e_and_r_vals(md_e,E_best_vals_from_md_r) which takes no input arguments. The fitness ...

6 dagar ago | 0

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