method

laplace_expansion

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What's this?

laplace_expansion(row: nil, column: nil) public

Returns the Laplace expansion along given row or column.

Matrix[[7,6], [3,9]].laplace_expansion(column: 1)
 => 45

Matrix[[Vector[1, 0], Vector[0, 1]], [2, 3]].laplace_expansion(row: 0)
 => Vector[3, -2]

Show source

# File lib/matrix.rb, line 645
  def laplace_expansion(row: nil, column: nil)
    num = row || column

    if !num || (row && column)
      raise ArgumentError, "exactly one the row or column arguments must be specified"
    end

    Matrix.Raise ErrDimensionMismatch unless square?
    raise RuntimeError, "laplace_expansion of empty matrix is not defined" if empty?

    unless 0 <= num && num < row_count
      raise ArgumentError, "invalid num (#{num.inspect} for 0..#{row_count - 1})"
    end

    send(row ? :row : :column, num).map.with_index { |e, k|
      e * cofactor(*(row ? [num, k] : [k,num]))
    }.inject(:+)
  end

laplace_expansion

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