method

rank

v1_9_3_125 - Show latest stable - 0 notes - Class: Matrix

rank() public

Returns the rank of the matrix. Beware that using Float values can yield erroneous results because of their lack of precision. Consider using exact types like Rational or BigDecimal instead.

Matrix[[7,6], [3,9]].rank
  => 2

Show source

# File lib/matrix.rb, line 1103
  def rank
    # We currently use Bareiss' multistep integer-preserving gaussian elimination
    # (see comments on determinant)
    a = to_a
    last_column = column_size - 1
    last_row = row_size - 1
    pivot_row = 0
    previous_pivot = 1
    0.upto(last_column) do |k|
      switch_row = (pivot_row .. last_row).find {|row|
        a[row][k] != 0
      }
      if switch_row
        a[switch_row], a[pivot_row] = a[pivot_row], a[switch_row] unless pivot_row == switch_row
        pivot = a[pivot_row][k]
        (pivot_row+1).upto(last_row) do |i|
           ai = a[i]
           (k+1).upto(last_column) do |j|
             ai[j] =  (pivot * ai[j] - ai[k] * a[pivot_row][j]) / previous_pivot
           end
         end
        pivot_row += 1
        previous_pivot = pivot
      end
    end
    pivot_row
  end

rank

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