Comparing two matriced

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joseph Frank
joseph Frank 2011-3-10
评论： Kiarash Ahi 2014-7-21
Hi,
Is there a fast way to compare the differences between two matrices with the same dimension:
example Assume A and B each is a 1000x1000 matrix. Is there a way to find where A and B differ in one step?

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回答（4 个）

Jan
Jan 2011-3-10
And if the matrices are results of floating point computation a certian relative or absolute tolerance might be helpful:
abs_d = (A - B) < Tol
rel_d = ((A - B) ./ min(A, B)) < Tol
And now the same tools as replied by Walter, Sean and Matt can be applied.
Walter Roberson
Walter Roberson 2011-3-10
find(A~=B)
Sean de Wolski
Sean de Wolski 2011-3-10
The logical matric
ABne = A~=B
or if you need the indices
[r c] = find(ABne);
Matt Fig
Matt Fig 2011-3-10
And a visual method:
spy(A~=B)
And a quick method to count the number of locations where A is not equal to B:
nnz(A~=B)
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Jan
Jan 2011-3-10
NNZ is *much* faster in SSE, especially if the data are aligned at 128 bit boundaries.
Sean de Wolski
Sean de Wolski 2011-3-10
I find it funny how the help for nnz says:
The density of a sparse matrix S is nnz(S)/prod(size(S))"
But M-Lint now says:
numel(S) is faster than prod(size(S))"

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