Actually, think I figured out an answer. I can just use repmat to create a matrix of n copies of the vector, and use == with the vector to compare it that way.
Produce equality matrix based on elements in vector.
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Given two equally sized vectors A and B, is there any way to make a matrix C of 1's and zero's such that the kth row of C contains 1's wherever elements of B equal the kth element of A?
I can do it by looping through elements of A, but I want to know if there's a vectorised way of doing this to speed it up?
2 Comments
Guillaume
on 27 Mar 2020
"I can just use repmat"
You don't need repmat. Implicit expansion will take care of repeating the elements for you and will be faster. See my answer.
Accepted Answer
Guillaume
on 27 Mar 2020
Trivially done.
%assuming A and B are both row vectors:
C = A.' == B;
If they're both column vectors, transpose B instead.
More Answers (3)
Bernd Wagner
on 27 Mar 2020
Does the Logical opperator C= A==B not do that work?
It compares values in Vector A and responds a logical value 1 if the Value is also on the same line in B. Hence your C vector will be a vector of 0 and 1 with 1 if A==B.
darova
on 27 Mar 2020
Try bsxfun
% make all combinations using bsxfun
C = bsxfun(@minus,b(:),a(:)'); % b - rows, a - columns
[i,j] = find(~C); % find 'zero'
C1 = C*0;
C1(i,:) = 1; % make entire row '1' if any element a==b
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