Fast matrices comparison

*To*: mathgroup at smc.vnet.net*Subject*: [mg115893] Fast matrices comparison*From*: JJ <wateronwildfire at gmail.com>*Date*: Tue, 25 Jan 2011 04:19:23 -0500 (EST)

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.