[ ruby ] group_byを使う ref: http://qiita.com/penguin_dream/items/179460ee63f7ca26a988

enumerable_groupby_sample01.rb

def evaluate_num(val)
  return "RED"  if val <= 2
  return "BLUE" if val > 3
end
(1..5).group_by {|x|
          evaluate_num(x)
       }
#=> {"RED"=>[1, 2], "BLUE"=>[3, 4, 5]}

#marks = {"Ramesh":23, "Vivek":40, "Harsh":88, "Mohammad":60}
def group_by_marks(marks, n)
    def evaluate(age, standard)
        return "Failed" if age < standard
        return "Passed" if age >= standard
    end
    marks.group_by{|k, v|
        evaluate(v, n)
    }
end
##=> {"Failed"=>[["Ramesh", 23]], "Passed"=>[["Vivek", 40], ["Harsh", 88], ["Mohammad", 60]]}

file1.txt

def evaluate_num(val)
  return "RED"  if val <= 2
  return "BLUE" if val > 2
end
(1..5).group_by {|x|
          evaluate_num(x)
       }
=> {"RED"=>[1,2], "BLUE"=>[3, 4, 5]}

これだと返却されるhashのキーを自分で決めることができない

(1..5).group_by {|x| x%2}
=> {1=>[1,3,5], 0=>[2, 4]}