From: dblack@...
Date: 2007-02-08T06:30:33+09:00
Subject: Re: histogram of histograms

Hi --

On Thu, 8 Feb 2007, Charles L. Snyder wrote:

> Hi
>
> I have several text files that look like this:
>
> Brazil,	10
> Brazil,	13
> Brazil,	9
> Bulgaria, 1
> Canada, 48
> Canada, 52
> Canada, 38
> Canada, 55
> Canada, 59
> Chile, 1
> Chile, 1
> Chile, 2
> China, 7
> China, 18
> China, 19
> China, 22
> China, 25
>
> I need to iterate through the above file(s) and get the data
> summarized in the form:
>
> Canada, 252
> China, 91
> Chile, 4
> Brazil, 32
> Bulgaria, 1
>
> I know how to go from a single column list with multiple repeated
> values to a 'histogram' type list, ie:
>
> my_hash = countries.inject(Hash.new { 0 }) { |counts, key| counts[key]
> += 1; counts}
> my_hash = my_hash.sort { |a,b| a[1] <=> b[1] }

my_hash will actually become an array at that point :-)

> but I'm unable to figure out how to get the 2-column csv values into a
> total by country as shown above.
> (I do have another file "countries.txt" which is a unique list of
> countries.)

Here's one way:

require 'scanf'

hash = Hash.new {0}
DATA.scanf("%s%d") {|key,count| hash[key] += count }

hash.sort.each {|k,v| puts "#{k} #{v}" }

__END__
Brazil, 10
Brazil, 13
Brazil, 9
Bulgaria, 1
etc.

That has the slight ugliness of including the comma in the key.  You
could do:

   hash[key.chomp(",")] += count

to avoid that, and then add the comma to the printout if you want it
back.


David

-- 
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