From: Drew Olson <olsonas@...>
Date: 2006-12-19T07:04:42+09:00
Subject: Output unique values in CSV columns to a text file

What I want to do is read in a CSV file and produce an output which
lists the unique values from each column in the following format:

Column: ColHeader1
   UniqueVal1
   UniqueVal2
Column: ColHeader2
   UniqueVal1
   UniqueVal2
...

What I'm currently getting is output that looks as follows:

Column: ColHeader1

   ColHeader1UniqueVal1
   ColHeader1UniqueVal2
Column: ColHeader2

   ColHeader2UniqueVal1
   ColHeader2UniqueVal2
...

For some reason, it is appending the column header to each value and
also printing a blank row to start each column. My code is below. Any
help is much appreciated. Essentially I read the CSV into a hash where
the key is the column header and the element is an array of values from
that column. I then run .uniq! on each array in the hash and print the
results to a file.

require 'rubygems'
require 'faster_csv'

infile = "xyz.csv"

uniques = {}

FCSV.open(infile, :headers => true).each do |row|
  row.each_with_index do |element,j|
    uniques[row.headers[j]] ||= []
    uniques[row.header[j]] << element
  end
end

uniques.each do |key,element|
  element.uniq!
end

File.open("unique_output.txt","w+") do |out|
  uniques.each_key do |key|
    out.write "Column: #{key}\n"
    uniques[key].each do |element|
      out.write "   #{element}\n"
    end
  end
end

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