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Ruby csv column sort

Posted on 2008-10-02
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Last Modified: 2012-08-13
Hello
Want to know how to sort by column asc or desc
Script is .......
require 'csv'  
  people = CSV.read("c:/foo.txt")
  joe = people.find_all {|person| person[0] =~ /Joe/}
 
#when writing back to file I want to sort by column 2 ascending (file has 3 columns)
  CSV.open("c:/fooreturn.txt","w") do |csv|
    joe.each do |person|
      csv <<person
    end
  end
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Question by:philsivyer
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Expert Comment

by:Geert Bormans
ID: 22626707
I suspect that what you need is the sort_by method,
like this
 joe = people.find_all {|person| person[0] =~ /Joe/}
 joe = joe.sort_by {|j| j[0]}

I assume that joe is an enumerable of some kind
likely it is an array of arrays

If this doesn't work, can you then post an example of foo.txt, so I can test,
thanks

Geert
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Expert Comment

by:Geert Bormans
ID: 22626794
yep, this works,
of course you will need this
  joe = joe.sort_by {|j| j[1]}
(so 1 instead of zero)
sorting on 'Joe' is not exciting enough :-)
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Author Comment

by:philsivyer
ID: 22628106
Thanks Gertone
Have you used Ruport and if so what do you think of it?

Phil
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Expert Comment

by:Geert Bormans
ID: 22628123
never used it, but I can a look tomorrow if you want.
I usually handle reporting with my own coding, but it could be wise to use ruport instead
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Author Comment

by:philsivyer
ID: 22628259
What sort of reports do you normally generate?
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Author Comment

by:philsivyer
ID: 22628334
Where would I put the reverse! so as to sort descending?
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Expert Comment

by:Geert Bormans
ID: 22628515
joe = joe.sort_by {|j| j[1]}.reverse!

I usually create reports in html (hacked together with ruby scripting)
so they can be viewed with a browser
often in different files, with links etc.
usually pretty  specific, hence my hacking mood instead of using something like ruport
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Author Comment

by:philsivyer
ID: 22632803
Gertone
How do you graph - do you use something like "scruffy"  - I deliver reports using Crystal Enterprise (Business Objects) and by developing sql scripts (stored procedures) which feeds data to Crystal.
Just interested in looking at other avenues such as your approach - any examples.
Phil
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Author Comment

by:philsivyer
ID: 22634303
Gertone
Final question:being playing around trying to return column 2 only to output file - without success.
How can you return selective columns - say in this case columns 1 & 3

Phil
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Accepted Solution

by:
Geert Bormans earned 250 total points
ID: 22643795
graphs:
various techniques used
- the svg library
- creating XML, than generating SVG using XSLT

I have not used scruffy

filtering out the second column... you can use a collect statement
  joe = people.find_all {|person| person[0] =~ /Joe/}
  joe = joe.sort_by {|j| j[1]}.reverse!
  joe.collect!{|arr| [arr[0] , arr[2]]}
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Author Comment

by:philsivyer
ID: 22645577
Thanks Gertone
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Expert Comment

by:Geert Bormans
ID: 22645582
welcome
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