Re: Matrix question

*To*: mathgroup at smc.vnet.net*Subject*: [mg60304] Re: [mg60287] Matrix question*From*: "David Park" <djmp at earthlink.net>*Date*: Sat, 10 Sep 2005 22:36:23 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Needs["DiscreteMath`Combinatorica`"] randommatrix[n_, p_] := Module[{worklist, numones = Floor[p n^2]}, worklist = Join[Array[1 &, numones], Array[0 &, n^2 - numones]]; worklist = Part[worklist, Ordering[RandomPermutation[n^2]]]; Partition[worklist, n]] randommatrix[4, 0.5] // MatrixForm First I made an array of the required number of 1's join to the remainder zeros. Then I made a random permutation of the list. Then I partitioned the list into rows. David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: sandog [mailto:sandog at mail.gr] To: mathgroup at smc.vnet.net i want to create a NxN matrix with zeros but i want a percentage of the matrix spots to be one at random spots any idea? cause i have no clue how to do that. Any help appreciated thx .