Splicing and Sorting problem with Tie::IxHash

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

Hi, I have a code that to pick upper-N value of a supposedly sorted hash - using Tie::IxHash.
But, why my code below give:

1-1:80
2-4:72
[download]

instead of:

1-2:2196
2-2:180
[download]

The reorder method I am using seems to be correct, has splicing part too. But why?
Thanks,
Edward

%hash = (
          '1-1' => 80,
          '1-4' => 26,
          '4-4' => 3,
          '2-2' => 180,
          '2-4' => 72,
          '1-2' => 2196
        );
  $N =2;
  %hash = seq_score($N,%hash); 
  printhash(%hash);

#---sub-----
sub seq_score{

  use Tie::IxHash;
  tie my %spair, "Tie::IxHash"; #modified

  ($N,%spair) = @_;
  my %topN_pair = ();
  my %seq =();

  my $t = Tie::IxHash->new(%spair);  #set new class
  $t->Reorder( reverse $t->SortByValue()->Keys() );#desc sort by value
   %topN_pair = $t->Splice(0, $N);                   
   return %topN_pair;
}

sub printhash
{
    my %hash = @_;
    
    foreach my $key (sort{$hash{$b}<=>$hash{$a}} keys %hash )
    {   next if ($hash{$key} <=1);
        print $key, ":", $hash{$key}, "\n"
    }                
}
[download]

Comment on Splicing and Sorting problem with Tie::IxHash Select or Download Code

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Re: Splicing and Sorting problem with Tie::IxHash by Limbic~Region (Chancellor) on Oct 06, 2004 at 12:56 UTC
ewijaya, Tie::IxHash's main focus is not sorting hashes, but preserving order. It does provide a couple of limited methods to sort the hash (by keys and values), but does not provide an interface to do a numerical sort. You likely want to use Tie::Hash::Sorted for this. See below: `#!/usr/bin/perl use strict; use warnings; use Tie::Hash::Sorted; my $sort = sub { my $hash = shift; [ sort {$hash->{$b} <=> $hash->{$a}} keys %$hash ]; }; tie my %hash, 'Tie::Hash::Sorted', 'Sort_Routine' => $sort; %hash = ( '1-1' => 80, '1-4' => 26, '4-4' => 3, '2-2' => 180, '2-4' => 72, '1-2' => 2196 ); Print_Top(2, \%hash); sub Print_Top { my ($max, $hash) = @_; for ( keys %$hash ) { return if ! $max--; print "$_ : $hash->{$_}\n"; } }` [download] Cheers - L~R	[reply] [d/l]
Re: Splicing and Sorting problem with Tie::IxHash by si_lence (Deacon) on Oct 06, 2004 at 07:41 UTC
Hello, I don't see excatly what you are trying to do (still morning here ...). But to print out just the top two keys of your hash based on the value I would use something like this: `use warnings; use strict; my %hash = ( '1-1' => 80, '1-4' => 26, '4-4' => 3, '2-2' => 180, '2-4' => 72, '1-2' => 2196 ); my $count=1; foreach my $key (sort{$hash{$b}<=>$hash{$a}} keys %hash ) { print "$key : $hash{$key}\n" ; last if $count++ > 1; }` [download] hth, si_lence	[reply] [d/l]
Re^2: Splicing and Sorting problem with Tie::IxHash by monkfan (Curate) on Oct 06, 2004 at 07:57 UTC
Hi, Thanks for the reply. But,I need top-'N' values, and still keep it as a hash.	[reply]
Re^3: Splicing and Sorting problem with Tie::IxHash by si_lence (Deacon) on Oct 06, 2004 at 10:10 UTC
OK. In this case I think you can make it without the tied hash. You will have to sort the output in printhash (as you did) to get them in descending order. si_lence %hash = ( '1-1' => 80, '1-4' => 26, '4-4' => 3, '2-2' => 180, '2-4' => 72, '1-2' => 2196 ); $N =2; %hash = seq_score($N,%hash); printhash(%hash); #---sub----- sub seq_score{ my %spair; ($N,%spair) = @_; my %topN_pair = (); my %seq =(); my $count=1; foreach my $key (sort{$spair{$b}<=>$spair{$a}} keys %spair ) { $topN_pair{$key}=$spair{$key}; last if $count++ >= $N; } return %topN_pair; } sub printhash { my %hash = @_; foreach my $key (sort{$hash{$b}<=>$hash{$a}} keys %hash ) { print $key, ":", $hash{$key}, "\n" } } [download]	[reply] [d/l]