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MathGroup Archive 2005

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Re: Matrix question

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


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

From: sandog [mailto:sandog at]
To: mathgroup at

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 .

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