method

determinant_e

v1_9_1_378 - Show latest stable - 0 notes - Class: Matrix

determinant_e() public

Returns the determinant of the matrix. If the matrix is not square, the result is 0. This method’s algorism is Gaussian elimination method. This method uses Euclidean algorism. If all elements are integer, really exact value. But, if an element is a float, can’t return exact value.

Matrix[[7,6], [3,9]].determinant
  => 63

Show source

# File lib/matrix.rb, line 717
  def determinant_e
    return 0 unless square?
    
    size = row_size - 1
    a = to_a
    
    det = 1
    k = 0
    loop do
      if a[k][k].zero?
        i = k
        loop do
          return 0 if (i += 1) > size
          break unless a[i][k].zero?
        end
        a[i], a[k] = a[k], a[i]
        det *= -1
      end

      for i in (k + 1)..size
        q = a[i][k].quo(a[k][k])
        k.upto(size) do |j|
          a[i][j] -= a[k][j] * q
        end
        unless a[i][k].zero?
          a[i], a[k] = a[k], a[i]
          det *= -1
          redo
        end
      end
      det *= a[k][k]
      break unless (k += 1) <= size
    end
    det
  end

determinant_e

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