Re: Matrix question

*To*: mathgroup at smc.vnet.net*Subject*: [mg60337] Re: Matrix question*From*: "Dr. Wolfgang Hintze" <weh at snafu.de>*Date*: Tue, 13 Sep 2005 06:07:35 -0400 (EDT)*References*: <dfudth$1qo$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, understanding that you are looking for a matrix in which a percentage p of random positions has the value 1 whereas the rest is 0 (same understanding as David Park and Bill Rowe) my solution (very straighforward, working without any package and for Version 4) is Parameters of the problem n = 10; p = 0.3; Init m = Floor[n^2*p]; A = Array[0 & , {n, n}]; Select a set of m random positions {i,j} r = {}; While[Length[r] < m, AppendTo[g, {1 + Random[Integer, n - 1], 1 + Random[Integer, n - 1]}]; r = Union[r]] Assign 1 to the random positions in matrix A Do[A[[r[[i,1]],r[[i,2]]]] = 1, {i, 1, Length[r]}] MatrixForm[A] Regards, Wolfgang sandog wrote: > 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 . > >