Module: HashRollup

Defined in:: lib/hash_rollup.rb

Overview

HashRollup

Author: Joel Parker Henderson, [email protected]
Copyright: Copyright © 2007-2009 Joel Parker Henderson
License: CreativeCommons License, Non-commercial Share Alike
License: LGPL, GNU Lesser General Public License

HashRollup aggregates value for a hash of hashes, for example to help calculate subtotals grouped by key.

Example:

h=Hash.new
h['a']=Hash.new
h['b']=Hash.new
h['c']=Hash.new
h['a']['x']=1
h['a']['y']=2
h['a']['z']=3
h['b']['x']=4
h['b']['y']=5
h['b']['z']=6
h['c']['x']=7
h['c']['y']=8
h['c']['z']=9
h.rollup => {"a"=>[1,2,3],"b"=>[4,5,6],"c"=>[7,8,9]}

Calculating subtotals

The rollup and rolldown methods can be useful for calculating subtotals by key.

Example:

h = h.rollup
r['a'].sum => 6
r['b'].sum => 15
r['c'].sum => 24

Instance Method Summary collapse

#rollup ⇒ Object

Instance Method Details

#rollup ⇒ `Object`

# File 'lib/hash_rollup.rb', line 42

def rollup
  a=self.class.new
  keys.each{|k| a[k]=self[k].values}
  a
end