From: William James <w_a_x_man@...>
Date: 2007-02-03T17:00:07+09:00
Subject: Re: Beginner questions: sorting csv files

On Feb 2, 9:53 pm, Michael Sc <michael.schat...@gmail.com> wrote:
> William James wrote:
> > On Feb 2, 4:26 pm, Michael Sc <michael.schat...@gmail.com> wrote:
> >> Thank you very much.  I did not realize  it was so simple.  Do you know
> >> how to  refer to prior lines to make calculations?
>
> >> --
> >> Posted viahttp://www.ruby-forum.com/.
>
> > a =
> > [ ['alloy', 1.414],
> >   ['malign', 1.732],
> >   ['smudge', 2.0],
> >   ['smack', 2.236]
> > ]
>
> > 0.upto( a.size - 2 ) {|i|
> >   puts "Change from line #{i} to line #{i+1}:\
> >   #{ (a[i+1][1] - a[i][1]) / a[i][1] * 100 }%"
> > }
>
> Thank you very much.  I just had one more question about this then.  How
> would I write this to its own csv file?
>
> require 'csv'
> outfile = File.open('newfile.csv', 'wb')
> x=CSV.open("oldfile.csv", "r")
> x.sort_by{|a| a.values_at( 2,0,1 ) }.each{|a| outfile.print a }
> outfile.close
>
> I tried outfile.p(doesn't work), outfile.print(takes out the commas) and
> outfile.put(takes out the breaks).  I know this should be incredibly
> easy but I am clearly missing something.

Before writing each record (i.e., each array of fields) to the file,
it must first be converted to a proper csv string.
The 'csv' package has a method for doing this, I presume.

If you don't wan't to use that, try this:


class Array
  def to_csv
    s = ''
    map { |item|
      str = item.to_s
      # Quote the string if it contains the field-separator or
      # a " or a newline or a carriage-return, or if it has leading or
      # trailing whitespace.
      if str.index( "," ) or /^\s|["\r\n]|\s$/.match(str)
        str = '"' + str.gsub( /"/, '""' ) + '"'
      end
      str
    }.join( "," )
  end
end

puts [ 674, "yes", "Jones,Tom", 'foo"bar', " space " ].to_csv

---  output  -----
674,yes,"Jones,Tom","foo""bar"," space "