# File lib/graphviz/math/matrix.rb, line 131
      def column( column )
        col = []
        unless (0...@column).to_a.include?(column-1)
          raise CoordinateError, "Column out of range (#{column} for 1..#{@column})!"
        end
        @line.times do |line|
          col << self[line+1, column]
        end
        
        return col
      end