From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2008-05-22T23:02:29+09:00
Subject: Re: Is rdoc (http://www.ruby-doc.org/core/) complete?

On Thu, May 22, 2008 at 3:11 PM, Victor Reyes <victor.reyes@gmail.com> wrote:
> Please forgive my ignorance and thank you for the information.
>
> I have an array of integers with a minimum of 9 elements and a maximum of
> 81.
> I need to count the frequency of each digit (1..9).
> That's why I was looking into the use of *find_all* or some other util that
> would make my code simple. Otherwise I would have to loop and count the old
> fashion way.
>

This is a typical way:

irb(main):001:0> a = [1,2,3,4,3,2,1,2,3,4,5,6,5,4,3,4,5,6,7,8,7,8,9]
=> [1, 2, 3, 4, 3, 2, 1, 2, 3, 4, 5, 6, 5, 4, 3, 4, 5, 6, 7, 8, 7, 8, 9]
irb(main):002:0> h = Hash.new {|h,k| h[k] = 0}
=> {}
irb(main):003:0> a.each {|x| h[x] += 1}
=> [1, 2, 3, 4, 3, 2, 1, 2, 3, 4, 5, 6, 5, 4, 3, 4, 5, 6, 7, 8, 7, 8, 9]
irb(main):004:0> h
=> {5=>3, 6=>2, 1=>2, 7=>2, 2=>3, 8=>2, 3=>4, 9=>1, 4=>4}

or:

irb(main):005:0> h2 = Hash.new(0)
=> {}
irb(main):006:0> a.each {|x| h2[x] += 1}
=> [1, 2, 3, 4, 3, 2, 1, 2, 3, 4, 5, 6, 5, 4, 3, 4, 5, 6, 7, 8, 7, 8, 9]
irb(main):007:0> h2
=> {5=>3, 6=>2, 1=>2, 7=>2, 2=>3, 8=>2, 3=>4, 9=>1, 4=>4}



Jesus.