# File lib/ruport/data/grouping.rb, line 281
    def summary(field,procs)     
      if procs[:order].kind_of?(Array)
        cols = procs.delete(:order) 
      else 
        cols = procs.keys + [field]   
      end
      expected = Table(cols) { |t|
        each do |name,group|
          t << procs.inject({field => name}) do |s,r|
            s.merge(r[0] => r[1].call(group))
          end 
        end
        t.data.reorder(cols)     
      }   
    end