Re: Vectorizing diagonalization of multiple matrices

[Brett Green]

On Tue, May 5, 2020 at 8:30 PM Nicholas Jankowski <address@hidden> wrote:

currently that code errors out for me:

parse error near line 6 of file C:\Users\nicholas.jankowski\Desktop\temp\test.m

  syntax error

>>>     [vecs(:,:,u,v),vals (:,:,u,v)] = eig(M(:,:,u,v));

if I delete the space between "vals ("  :

x = linspace(0,1,5);

y = linspace(2,3,5);

for u=1:5

for v=1:5

M = [ y(v)*x(u) , x(u) ;  x(u) , -y(v)^2 ];

[vecs(:,:,u,v), vals(:,:,u,v)] = eig(M(:,:,u,v));

end

end

then I get:

error: M(_,_,_,2): but M has size 2x2
error: called from
    test at line 6 column 36

My bad - I started writing this question, tried the MWE, noticed that it didn't work, fixed the code... and apparently forgot to copy the correct code back into the e-mail.

The corrected code is copied below.

x = linspace(0,1,5);
y = linspace(2,3,5);
for u=1:5
for v=1:5
M(:,:,u,v)=[y(v)*x(u),x(u);x(u),-y(v)^2];
[vecs(:,:,u,v),vals(:,:,u,v)] = eig(M(:,:,u,v));
end
end

The space after vals must have been a typo after I copied this to Gmail. Aside from that, the only change is that I added (:,:,u,v) after M inside the loop.

When I copy this code out of Gmail. it appears garbled in both Notepad++ and Octave both, so there's probably something strange going on with the formatting. To circumvent that, I also attached the script.

 

test.m
Description: application/vnd.wolfram.mathematica.package