Better way to accumulate totals

ruby-talk
1

Thank you for the very clear and helpful explanation!

···

------------------------------
Robert Keller
rlkeller@yahoo.com

----- Original Message ----
From: 7stud -- <bbxx789_05ss@yahoo.com>
To: ruby-talk ML <ruby-talk@ruby-lang.org>
Sent: Tuesday, October 30, 2007 5:20:12 PM
Subject: Re: better way to accumulate totals

Robert Keller wrote:

The data lines look like this:

" category value"

case top_event[0].lstrip.rstrip
    when "Redo size:"

            $redo_cnt[0] += 1
            $redo_cnt[1] += top_event[1].to_f

    when "Logical reads:"

            $log_read_cnt[0] += 1
            $log_read_cnt[1] += top_event[1].to_f

This might be easier to understand:

#Create a hash, so that when you use a
#key that doesn't exist, it creates the key,
#assigns it the array [0,0], and returns the
#array:
categories = Hash.new() do |hash, key|
  hash[key] = [0,0]
end

#Loop over each line in a file:
File.foreach("data.txt") do |line|
  arr = line.split(":")
  cat = arr[0].strip
  val = Float(arr[1]) #causes an error if can't convert

  categories[cat][0] += 1
  categories[cat][1] += val
end

p categories
puts categories["Make pie"][0]
puts categories["Redo size"][1]

Using this data:

Redo size: 1.1
Logical reads: 2.1
Redo size: 1.1
Hello world: 3.1
Make pie: 4.1
Hello world: 3.1
Make pie: 4.1
Make pie: 4.1

this is the output:

{"Make pie"=>[3, 12.3], "Hello world"=>[2, 6.2], "Redo size"=>[2, 2.2],

"Logical reads"=>[1, 2.1]}
3
2.2
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