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Fast matrices comparison


Hi MathGroup

I have to compare two big matrices (in the SparseArray form), say m1 and m2.
I need that the elements of m1 will be replaced by 0 if they are less or
equal to
the corresponding elements of m2.

For example, if m1={{8,7},{3,9}} and m2={{2,3},{4,5}},
I would like to have m1={{8,7},{0,9}} because m1[[2,1]]<m2[[2,1]].

I can do it easily with two nested for loops but I think it is not an
efficient way to do it.
I was wondering if somebody knows how to do it using a fast conditional
replacement rule and/or pure functions.

Thank you.



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