From: Wilson Bilkovich <wilsonb@...>
Date: 2006-10-21T00:41:04+09:00
Subject: Re: problem with reading file

On 10/20/06, Li Chen <chen_li3@yahoo.com> wrote:
> Hi folks,
>
> I read a file in the following format,extract the second column only,
> and push them into an array. My problem is that Ruby reads them as
> strings(based on array.inspect) but not as numbers so it is impossible
> for me to do the calculation. Any comments?
>
> Thanks,
>
> Li
>
> ###filen name: array.text
>
>
> A       1       B
> A       2       B
> A       3       B
> A       4       B
> A       5       B
> A       6       B
>
> ...
>
> ###script
>
> equire 'enumerator'
>
> array=Array.new
>
> File.open('array.text').each{|line|  array<<line.split(/\t/)[1]}
>
> #puts array.inspect
> array.each_slice(3){|slice|
>                    average=(slice[0]+slice[1]+slice[2])/(3.0)
>                    puts average
>                 }
>
> ###output from screen
>
> C:/Ruby/self/file6.rb:8: undefined method `/' for "123":String
> (NoMethodError)
>         from
> c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
> `each_slice'
>         from C:/Ruby/self/file6.rb:7:in `each'
>         from C:/Ruby/self/file6.rb:7:in `each_slice'
>         from C:/Ruby/self/file6.rb:7
>

You need to tell Ruby to coerce the strings into integers.

array = []

File.open('array.text') do |file|
  file.each_line do |line|
    array << line.split[1].to_i
  end
end

array.each_slice(3) do |triplet|
  average = (slice[0]+slice[1]+slice[2])/3.0
  puts average
end