ruby , Reading a specific column of data from a text file in Ruby

Question:

Tag: ruby

I have tried Googling, but I can only find solutions for other languages and the ones about Ruby are for CSV files.

I have a text file which looks like this

0.222222 0.333333 0.4444444 this is the first line.

There are many lines in the same format. All of the numbers are floats.

I want to be able to read just the third column of data (0.444444, the values under that) and ignore the rest of the data.How can I accomplish this?

You can still use CSV; just set the column separator to the space character:

require 'csv'

CSV.open('data', :col_sep=>" ").each do |row|
puts row[2].to_f
end


You don't need CSV, however, and if the whitespace separating fields is inconsistent, this is easiest:

File.readlines('data').each do |line|
puts line.split[2].to_f
end


I'd recommend breaking the task down mentally to:

1. How can I read the lines of a file?
2. How can I split a string around whitespace?

Those are two problems that are easy to learn how to handle.

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