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How do i generate a 4 x 5 matrix full of random numbers with ruby 1.8.7
m_rand = Matrix #create an empty matrix

n = 0
for n in 0...5
    m=0
    for m in 0...4
        m_rand[n,m] = rand()
    end
end

m_rand = Array.new(4){Array.new(5){rand} }

require 'matrix'

rows = (0...5).map do
  (0...4).map do
    rand()
  end
end

m_rand = Matrix[rows]

Matrix.build(rows, cols) { |row, col| rand }