Re: Two questions about modification of a matrix.

*To*: mathgroup at smc.vnet.net*Subject*: [mg101052] Re: [mg101041] Two questions about modification of a matrix.*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Tue, 23 Jun 2009 07:02:25 -0400 (EDT)*Reply-to*: hanlonr at cox.net

mat = Table[RandomReal[{-1, 1}], {7}, {5}] mat2 = mat*Table[If[i*j > 6, 0, 1], {i, Length[mat]}, {j, Length[mat[[1]]]}] mat3 = Map[Max[0, #] &, a, {2}] Bob Hanlon ---- Mayasky <alix.zhang at gmail.com> wrote: ============= Suppose there is a N*N matrix. 1. How can I change all elements that satisfy i*j>N to 0 ? (Here i, j is position of this element, as in mat[[i,j]]) 2. How can I change all negative elements in that matrix to 0 ? I know a "for loop" can be used, I just wonder if there is any more concise and beautiful ways. (I doubt Mathematica doesn't have a 'find' function as in another system which conveniently returns indice of elements that satisfy a certain condition)