Question

I have a specific problem that I just can’t find a solution for.
I get data in the following format from a text file

    date1 reason1
    date1 reason1
    date1 reason2
    date1 reason3
    date2 reason4
    date2 reason1
    date2 reason2
    date2 reason2
    date2 reason1
    date2 reason3
    date3 reason4
    date3 reason4
    date3 reason1

I want to build statistics on the data e.g. I want to count all different “reasons” from each date like this

    date1 reason1 -> 2        
    date1 reason2 -> 1
    date1 reason3 -> 1
    date2 reason1 -> 2
    date2 reason4 -> 1
    date2 reason2 -> 2
    date1 reason3 -> 1

…and so on. How would I parse the data and build the required result? I guess hashes would be used but I failed to imagine a way to solve this.

Answer 1

Here’s a very straight forward approach:

h = Hash.new(0)
File.foreach("foo.txt") do |line|
  h[line.chomp] += 1  
end  
h
#=> {"date1 reason1"=>2,
 "date1 reason2"=>1,
 "date1 reason3"=>1,
 "date2 reason4"=>1,
 "date2 reason1"=>2,
 "date2 reason2"=>2,
 "date2 reason3"=>1,
 "date3 reason4"=>2,
 "date3 reason1"=>1}