# Comparing two matrices, and acting upon the result element by element.

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Matt on 11 Dec 2011
Hi All,
I have two large 2D matrices, A and B of equal dimensions, containing integer values.
What I would like to do is if the value of the element in A is equal to a specific value, then use the value from B, but otherwise leave the value of A unchanged. I am pretty certain this should be simple to implement but I have hit a brick wall in my competence.
Thank you very much!
M
(I have found a way of doing this with a dreadfully inefficient bash script, but this takes literally days to run, as it involves lots of temporary files etc. There are also ways I have fond in previous answers that come close to solving it, but I can't find anything specific enough that I can successfully adapt it.)

Paulo Silva on 11 Dec 2011
A=randi(5,3,3)
B=10*randi(5,3,3)+5
A(A==v)=B(A==v) %replace elements of A equal to v by B ele. on same position
Matt on 12 Dec 2011
Perfect, thank you very much!