Extend a matrix by extending its vectors
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f10w
el 29 de Mayo de 2014
Comentada: f10w
el 30 de Mayo de 2014
I have an d*m*n matrix A (interpretation: for each n, there are m vectors of dimension d). I would like to extend each d-dimensional vector as follows:
Consider a vector of dimension d: (1,2,...,d) (it's (x_1,x_2,...,x_n) but I removed the 'x_' for simplicity). The goal is to extend v to obtain a d*d vector of the form:
(1,1,...,1,2,...,2,...,d,d,...,d)
There are several ways to extend a single vector, as already suggested here. Suppose that a function called 'extend' does that job. Then, to extend every vector in the matrix A, we can do:
B = zeros(d*d,m,n);
for i = 1:n
for j = 1:m
B(:,j,i) = extend(A(:,j,i);
end
end
However, this is quite slow because of the loop. Could anybody please suggest me a fast way to do that?
Thank you in advance for your help.
2 comentarios
José-Luis
el 29 de Mayo de 2014
What makes you thing it's slow because of the loop? Not all loops are evil. It would depend on what your extend() function looks like.
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