How to load a CSV with two columns in Ruby and save it in 2 arrays

Question

I want to load a CSV-file with two columns (each with a name and a row of numbers) and save only the numbers of the two columns in two different arrays. Then I want to make some calculations with the data in those two columns, using two arrays to save the numbers of each column.

This is what I still have:

require 'csv'
filename = 'file.csv'
csv_data = CSV.read(filename, :col_sep => ";")
csv_data.shift
csv_data.each_with_index { |column, index_c|
  average = 0
  column.each_with_index{ |element, index_e|
    csv_data[index_c][index_e] = element.to_i
  }
}
csv_data = csv_data.transpose

How can I split the columns of csv_data in two arrays ?

Can you include an example of what the CSV file looks like and what output you're looking for? — mu is too short
– mu is too short, Commented Apr 6, 2012 at 20:27
the csv looks like: data1 data2 1 5 2 6 3 7 4 8 i need each column in one single array. here arr1, including (1,2,3,4), and arr2 including (5,6,7,8). — jeffrey
– jeffrey, Commented Apr 6, 2012 at 20:33

dbenhur · Accepted Answer · 2012-04-06 21:19:22Z

3

This should do the trick for you creating your two column arrays without wasting storage reading the whole file redundantly into csv_data.

require 'csv'
filename = 'file.csv'
arr1 = []
arr2 = []
CSV.foreach(filename, :col_sep => ";", :return_headers => false) do |row|
  arr1 << row[0].to_i
  arr2 << row[1].to_i
end

edited Apr 6, 2012 at 21:19

answered Apr 6, 2012 at 21:00

dbenhur

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2 Comments

jeffrey Over a year ago

now I have the problem, that I want to calculate the yield by arr1.each_cons(2) { |c| arr3.push(Math.log(c[1]/c[0]))}. there is the error: divided by 0, but why? where is the mistake?

dbenhur Over a year ago

I would presume because one of the values is arr1 is 0 and c[1]/c[0] raises ZeroDivisionError. arr1.each_with_index{|v,i| puts "found zero at index #{i}" if v == 0 }

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