Matrices multiplication in a loop
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Hello
I have many matrices in two categories say M_i and N_j generated in a for loop. They all have order 2*2. I want to conv each M_i with every N_j i.e.
conv(M_1, N_1)
conv(M_1, N_2) ...
then:
conv(M_2, N_1)
conv(M_2, N_2)...
Any help?
5 个评论
Rik
2019-7-25
Why did you use numbered variables? This would be trivial with a nested loop if you had stored them in a cell array.
The best solution is going one step back and not use numbered variables.
Stephen23
2019-7-25
"I have many matrices ... say M_i and N_j generated in a for loop..."
And that is the bad design decision right there.
If you had simply used indexing (in an ND numeric array or a cell array), then resolving your question would be trivial (hint: by also using indexing). But by creating lots of separate matrices, you will force yourself into writing slow, complex, obfuscated, buggy code that is hard to debug. Read this to know some of the reasons why:
https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval
In contrast, indexing is neat, simple, easy to understand, easy to debug, and very efficient (unlike what you are trying to do). You should use indexing.
TADA
2019-7-25
doesn't conv accept only 1 dimentional vectors?
Also, if you instantiate 2 3D matrices instead of ixj 2D matrices your life would be easier:
% preallocate:
N = zeros(2,2,n);
M = zeros(2,2,m);
% where n and m are the number of matrices you instantiate today using i and j
% assuming that m ~= n:
for i = 1:n
% N(:,:,i) = whatever calculation you do today
end
for j = 1:m
% M(:,:,j) = whatever calculation you do today
end
tanveer haq
2019-7-25
tanveer haq
2019-7-25
编辑：tanveer haq
2019-7-25
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2019-7-25
2019-7-25
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