# File lib/ruport/data/table.rb, line 466
    def swap_column(a,b)    
      if [a,b].all? { |r| r.kind_of? Fixnum }
       col_a,col_b = column_names[a],column_names[b]
       column_names[a] = col_b
       column_names[b] = col_a
      else
        a_ind, b_ind = [column_names.index(a), column_names.index(b)] 
        column_names[b_ind] = a
        column_names[a_ind] = b
      end
    end