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Sorting Complex Data Structure

by Anonymous Monk
on Jan 21, 2014 at 12:43 UTC ( #1071462=perlquestion: print w/replies, xml ) Need Help??

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Dear keepers of Perl knowledge,

I'm working with a quite complex data structure (I think it's a array of arrays of hashes) and I need sort the results before printing. I can access each element by using @Data[$_]{ID}, @Data[$_]{Score} and looping through the number of elements.

The issue lies in the fact that I need to sort by Score and then group the results of same IDs together based on the score of the top hit with a given ID. Example:

ID: AA Score: 20 ID: D Score: 30 ID: F Score 7 ID: AA Score: 3

The results should look like:

ID: D Score: 30 ID: AA Score: 20 ID: AA Score: 3 ID: F Score 7

I thought about creating additional, separate hash, sorting by score, printing the 1st one and looping looking for all other with same ID (I would need to delete everything I use in the process to avoid redundancies). I presume there must a more straight forward and elegant solution. Thanks for your help.

Replies are listed 'Best First'.
Re: Sorting Complex Data Structure
by choroba (Archbishop) on Jan 21, 2014 at 13:27 UTC
    Creating a hash is a good way. You can sort the result for each id, so you do not have to search for the same ids.
    my %by_id; push @{ $by_id{ $_->{id} } }, $_->{score} for @data; # Sort the scores for each id. $_ = [ sort { $b <=> $a } @$_ ] for values %by_id; # Sort the ids by the highest score. for my $id (sort { $by_id{$b}[0] <=> $by_id{$a}[0] } keys %by_id) { print "ID: $id\tScore: $_\n" for @{ $by_id{$id} }; }
    لսႽ ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

      Hi choroba,

      Thanks that seemed to do the trick. The remaining issue is that I have a lot of other features saved in the original data structure (that varies depending on task). Is there a way to perhaps link this with the original array indexes, save the order and then print it using this order? Thanks again

Re: Sorting Complex Data Structure
by Corion (Patriarch) on Jan 21, 2014 at 13:20 UTC
Re: Sorting Complex Data Structure
by ww (Archbishop) on Jan 21, 2014 at 14:15 UTC
    "I think it's a array of arrays of hashes"

    Perhaps you should use Data::Dumper or some other technique to confirm or rebut that thought.

      ww++. This is the only reasonable answer ... until you know what the data structure is, all the other solutions are just throwing code at the wall to see what sticks.

      -derby
      Hi, I've used the data dumper before - it's array of array of hashes and chorobas code works. Thanks

        From the OP:

        I can access each element by using @Data[$_]{ID}, @Data[$_]{Score}...

        I assume this was a misprint for $Data[$_]{ID}, $Data[$_], since you are accessing single elements, not array slices.

        it's array of array of hashes and chorobas code works.

        Here is how choroba’s code works for me:

        use strict; use warnings; my @data = ( { ID => 'AA', Score => 20 }, { ID => 'D', Score => 30 }, { ID => 'F', Score => 7 }, { ID => 'AA', Score => 3 }, ); ## choroba's solution: my %by_id; push @{ $by_id{ $_->{ID} } }, $_->{Score} for @data; # Sort the scores for each id. $_ = [ sort { $b <=> $a } @$_ ] for values %by_id; # Sort the ids by the highest score. for my $id (sort { $by_id{$b}[0] <=> $by_id{$a}[0] } keys %by_id) { print "ID: $id\tScore: $_\n" for @{ $by_id{$id} }; }

        As you can see, there is only one array; i.e., @data is an array of hashes (AoH).

        Hope that helps,

        Athanasius <°(((><contra mundum Iustus alius egestas vitae, eros Piratica,

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