How to sort by the key value of an Array of Hash structure?

Jordy224 has asked for the wisdom of the Perl Monks concerning the following question:

Greetings, I have designed an Array of Hash - with the following representative structure:

@array  [0]   %Hash { name => proteobacteria, 
                            size => 30
              [1]   %Hash { phylum => alphabacteria,  
                            size => 50  
              [2]   %Hash { name => cytophaga,   
                            size => 10
[download]

... Question: How do I sort the array by the value of the hash key “size" Such that it is arranged in a new array in descending order? ie.

 @newarray [0]  %Hash {name => alphabacteria
                       size => 50
[download]

so far my script looks as follows...

@newarray = sort {$$hash{$b} <=> $$hash{$a} } @array, keys %Hash;

Thanks In advance.

Comment on How to sort by the key value of an Array of Hash structure? Select or Download Code

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Re: How to sort by the key value of an Array of Hash structure? by moritz (Cardinal) on Jul 30, 2008 at 16:25 UTC
Remember that `$a` and `$b` are the array items that are being sorted, in your case hash references. So you need to access the `size` key if you want to sort by it: `@newarray = sort { $b->{size} <=> $a->{size} @array;` If you want to see your data structures, I recommend Data::Dumper.	[reply] [d/l] [select]
Re: How to sort by the key value of an Array of Hash structure? by whakka (Hermit) on Jul 30, 2008 at 17:04 UTC
Stolen from this Q&A node, you can do a Schwartzian Transformation by doing: `my @sorted = map{ $_->[1] } sort { $b->[0] <=> $a->[0] } map{ [ $_->{size}, $_ ] } @{$aoh}; print Dumper \@sorted;` [download]	[reply] [d/l]
Re^2: How to sort by the key value of an Array of Hash structure? by kyle (Abbot) on Jul 30, 2008 at 17:56 UTC
Unless the "hashes" are actually tied or overloaded objects with really slow access times, I expect moritz's much simpler `sort { $a->{size} <=> $b->{size} }` will also be faster (but I'm ready to be corrected).	[reply] [d/l]
Re: How to sort by the key value of an Array of Hash structure? by dwm042 (Priest) on Jul 30, 2008 at 18:19 UTC
I rearranged your structure a little bit, for clarity, and you are awfully close to sorting it. For example: `#!/usr/bin/perl -w use strict; my @array = ( { name => "proteobacteriai", size => 30 }, { phylum => "alphabacteria", size => 50 }, { name => "cytophaga", size => 10 }, ); for (@array) { print "Size (out of order) = ",$_->{size}, "\n"; } my @newarray = sort { $a->{size} <=> $b->{size} } @array; for (@newarray) { print "Size = ",$_->{size}, "\n"; }` [download] yields `C:\Code>perl sort_aoh.pl Size (out of order) = 30 Size (out of order) = 50 Size (out of order) = 10 size = 10 size = 30 size = 50` [download]	[reply] [d/l] [select]