I am using two arrays (one that holds keys and one that holds values) to build a hash in Perl. I need to count and delete the repeated key/value pairs so that I have a unique hash. Then I have to build a hash of hashes of the form: ((key,value), count).
I am using this line to build the hash from the arrays.
@hash{@keys} = @values;
This will keep repeated key/value pairs in the hash which I do not want. Any help in creating the hash of hashes is appreciated. Thanks.
You can use a hash of hashes, where each key hash a subhash of the form value => count.
#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
my @keys = qw( k1 k1 k1 k2 k2 k3 k4 k4 k5);
my @values = qw( v1 v2 v2 v3 v4 v5 v6 v6 v7 );
my %hash;
for my $idx (0 .. $#keys) {
$hash{ $keys[$idx] }{ $values[$idx] }++;
}
print Dumper \%hash;
Let's say you arrays look like this:
my @keys = qw/a b c a a/;
my @values = qw/1 2 3 4 1/;
It's as easy as a simple for loop:
for ($i = 0; $i < scalar @keys; $i++) {
$hash{$keys[$i]}{$values[$i]} += 1;
}
You can then iterate over the inner values (the count) with a nested loop:
foreach my $key (keys %hash) {
while (my ($value, $count) = each %{ $hash{$key} } ) {
print "$key : $value = $count\n";
}
}
Which would produce:
c : 3 = 1
a : 4 = 1
a : 1 = 2
b : 2 = 1
You can sort the keys if you want to:
foreach my $key (sort keys %hash) {
# same as before
}
To get
a : 4 = 1
a : 1 = 2
b : 2 = 1
c : 3 = 1
((key,value), count)). A Key/Value pair can't be a hash key, has to be a string - Mathias R. Jessen