Matt J

Last seen: Today | Active since 2009

Professional Interests: medical image processing, optimization algorithms

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Answered
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...

16 hours ago | 0

Answered
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...

1 day ago | 0

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

2 days ago | 0

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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 days 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 days 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 days ago | 0

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How can I increase the number of Fourier frequencies by adding 500 zeros to the end of the 27-sample-long signal ??
L = length(t)+500; fftx1=fft(x1, L)

4 days ago | 0

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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 days ago | 1

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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 days ago | 0

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

4 days ago | 0

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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 days ago | 0

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

4 days ago | 0

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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 days ago | 0

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How to get rid of this line that connects the last and first point, I have made it white so its barely visible, but is there a way to not plot it?
plot3 (WayPTS(:,1), WayPTS(:,2), WayPTS(:,3),'black');

4 days 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 days ago | 0

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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 days ago | 0

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Answered
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 days ago | 0

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Answered
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 days ago | 1

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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 days ago | 0

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Answered
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 days ago | 0

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Answered
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 days ago | 0

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Answered
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 days ago | 0

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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 days 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 days 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 days ago | 0

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Answered
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 days ago | 0

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Answered
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 days ago | 1

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Answered
Rounding errors when using quadprog
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 days ago | 0

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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 days ago | 0

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Answered
Is there an alternative to eval in a struct?
Your data organization seems like it should be reconsidered. In a struct, it doesn't make sense if different fields have essenti...

7 days ago | 0

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