From: Robert Klemme <bob.news@...>
Date: 2003-10-01T16:40:10+09:00
Subject: Re: Array and hash iteration questions


"Ben Giddings" <bg-rubytalk@infofiend.com> schrieb im Newsbeitrag
news:3F79D516.9050509@infofiend.com...
> I have a CSV file and I'm trying to do a few things with it.
Essentially
> what it boils down to is: count the number of times a certain value is
> seen, then count the number of times another value is seen in
conjunction
> with the first one.
>
> I'm iterating over the lines of the file, and splitting them into an
array
> with arr = line.split(/,/).  That part works well, but there are a few
> questions about how to do something efficiently.
>
> In order to count the number of times something is seen, I took the
approach:
>
> cases = Hash.new(0)
> ..
>    cases[arr[324]] += 1
> ..
>
> But now I want to save the number of cases where another value occurs
with
> the first one.  (Essentially errors indexed by case)
>
> The approach I have now is:
>
> cases = Hash.new(0)
> errors = Hash.new(0)
> ..
>    case = arr[324]
>    cases[case] += 1
>    if arr[532] =~ /Error/
>      errors[case] += 1
>    end
> ..
>
> That works, but it seems to me that I really should be doing this with
one
> hash, not two.  Any suggestions?

cases = Hash.new {|h,k| h[k] = [0, 0]}
...
   ca = arr[324]
   counter = cases[ca]
   counter[0] += 1

   counter[1] += 1 if /Error/ =~ arr[532]

> Next, I want to print out the values.  It is easy to do this with
> cases.each, but I'd like to print them out, sorted by case.  The best
> solution I have so far uses cases.keys.sort.each, then inside the block
> uses cases[key] (and errors[key]).

cases.sort.each do |ca, counter|
  printf "%10s: %4d", ca, counter[0]
  printf " %4d", counter[1] if counter[1] > 0
  print "\n"
end

Regards

    robert