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)