# File lib/graphviz/math/matrix.rb, line 163
      def remove_line(n)
        unless (0...@line).to_a.include?(n-1)
          raise CoordinateError, "Line out of range (#{n} for 1..#{@line})!"
        end

        matrix = GraphViz::Math::Matrix.new( @line - 1, @column )
        nline = 0
        @line.times do |line|
          next if line == n - 1
          @column.times do |column|
            matrix[nline+1, column+1] = self[line+1, column+1]
          end
          nline += 1
        end
        return matrix
      end