Vectorizing Calculation of the Autocorreltion function of a Matrix (Per Column)

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Royi Avital
Royi Avital on 27 Jul 2011
Answered: Royi Avital on 11 Sep 2014
Hello.
I have a matrix
A = [1 2 3; 4 5 6; 7 8 9];
I want to calculate the Autocorrelation function of each of its columns.
Simple way to do so:
for ii = 1:size(A, 2)
autocorrelationFunction(:, ii) = conv2(A(:, ii), A(end:-1:1, ii));
end
Could anyone think of a vectorized way of doing so?
Thanks.

Accepted Answer

Royi Avital
Royi Avital on 11 Sep 2014
It can be done using Toeplitz matrix.

More Answers (1)

Daniel Shub
Daniel Shub on 27 Jul 2011
Wow, it is like a vectorization party in here today. Why do you want to vectorize your code? In recent years MATLAB has substantially sped up loops. If you are not using r2011a, you could speed up your loop by initializing autorcorrelationFunction to the correct size (r2011a has supposedly cut down on the cost of not pre-allocating arrays). You might be able to get a speed increase out of vectorization, but it may not be as big as you expect.
  1 Comment
Royi Avital
Royi Avital on 27 Jul 2011
I know all / most the acceleration methods when dealing with loops.
I'm looking for something which removes the loop completely.
Thank you.

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