Processing some CSV files for some Psychology PhD statistics work

multi_csv_processor.rb

require 'csv'

# Iterate through each CSV file in the current folder
Dir.glob('*.csv') do |csv_filename|
    # Create and open a new file to store the modified rows
    csv_output_file = CSV.open("modified-#{csv_filename}", 'wb')
    # Open the current file by filename
    CSV.open(csv_filename, 'r') do |csv_contents|
        # Iterate through each row in the CSV file
        csv_contents.each do |row|
            # Assign the row being read to a new row
            output_row = row
            # Fetch the column index we are interested in (offset by 1 based)
            target_index = row[5]
            # Fetch the value we are interested in given the index above
            target_value = row[target_index.to_i - 1]
            # Append the value as an additional column in the row
            output_row << target_value
            # Write the row to the output file
            csv_output_file << output_row
        end
    end
end