From: James Gray <james@...>
Date: 2008-12-04T05:07:33+09:00
Subject: Re: FasterCsv writing columns

On Dec 3, 2008, at 11:15 AM, Mordechai Mr wrote:

> Hi,

Hello.

> Can someone help me with FCSV writing ?

I'll sure try.

> If I have an array of integers lets say
> someList[0].listName = "header1"
> someList[0].someArray = [ 2, 4, 8, 9 ]
>
> someList[1].listName = "header2"
> someList[1].someArray = [ 10, 11, 12, 13 ]
>
> I'm desperately trying to figure out how to use FasterCSV to produce a
> csv file that will show:
>
> header1, header2
> 2,  10,
> 4,  11,
> 8,  12,
> 9,  13,
> header1_avg,header2_avg

I would use code like:

#!/usr/bin/env ruby -wKU

require "rubygems"
require "faster_csv"

Column  = Struct.new(:header, :data) do
   def average
     return 0 if data.empty?
     data.inject(0) { |sum, n| sum + n } / data.size
   end
end
columns = [ Column.new("header1", [2, 4, 8, 9]),
             Column.new("header2", [10, 11, 12, 13]) ]

FCSV do |csv|
   csv << columns.map { |c| c.header }
   columns.map { |c| c.data.size }.max.times do |i|
     csv << columns.map { |c| c.data[i] }
   end
   csv << columns.map { |c| c.average }
end

__END__

That spits the data to STDOUT.  If you would rather send it to a file,  
just change this line:

FCSV do |csv|

to:

FCSV.open("my_file_name.csv", "w") do |csv|

> I've read through the FasterCSV documents, and I just can't figure
> things out.  I know I most likely need to use the FCSV table, or read
> the array in and use the FCSV.parse...

Na.  These methods are for reading CSV data, not writing it.

Hope that helps.

James Edward Gray II