From: James Edward Gray II <james@...>
Date: 2007-02-06T22:35:54+09:00
Subject: Re: How do you get the rows out of FasterCSV?

On Feb 5, 2007, at 11:58 PM, ara.t.howard@noaa.gov wrote:

> require 'rubygems'
> require 'fastercsv'
>
> csv = <<-csv
> f,x
> a,0
> b,1
> c,2
> d,3
> csv
>
> fcsv = FasterCSV.new csv, :headers => true
> table = fcsv.read

Or just:

table = FCSV.parse(csv, :headers => true)

> xs = table['x'].map{|x| x.to_i}

When you want to convert a field, ask FasterCSV to do it for you  
while reading.  This changes the above to:

table = FCSV.parse(
   csv,
   :headers    => true,
   :converters => lambda { |f, info| info.header == "x" ? f.to_i : f }
)

Or using a built-in converter:

table = FCSV.parse(csv, :headers => true, :converters => :integer)

> sum = Float xs.inject{|sum,i| sum += i}

This is now simplified to:

sum  = Float table['x'].inject{|sum,i| sum += i}

> norm = xs.map{|x| x / sum}
>
> table['n'] = norm
> puts table

James Edward Gray II