From: Martin DeMello <martindemello@...>
Date: 2009-02-04T23:27:12+09:00
Subject: Re: Hash counting

On Wed, Feb 4, 2009 at 12:04 AM, Stuart Clarke
<stuart.clarke1986@gmail.com> wrote:
>
>        counts = Hash.new(0)
>        eventdateID.each {|d| counts[d] += 1}

Here is your problem. Hash.new(0) means "when I query the hash, and
the key I request is not in there, return 0". It does not actually add
{key => 0} to the hash itself. To do that, you need the block form of
Hash.new, which yields as block the hash itself and the key:

counts = Hash.new {|h, k| h[k] = 0}

irb(main):001:0> a = Hash.new(0)
=> {}
irb(main):002:0> b = Hash.new {|h,k| h[k] = 0}
=> {}
irb(main):003:0> a['hello']
=> 0
irb(main):004:0> b['hello']
=> 0
irb(main):005:0> a
=> {}
irb(main):006:0> b
=> {"hello"=>0}

martin