in reply to How to extract a row or column of two-dimensional hash

Welcome to the Monastery.

It is difficult to read your code without code tags. See Writeup Formatting Tips.

The code you provided does not compile due to a few syntax errors:

Is it possible for you to show a little of the structure and contents of BodyTemp? You could do this with: 

use Data::Dumper;
print Dumper(\%BodyTemp);

[download]

You may also find HASHES OF HASHES helpful in figuring out how to access this type of data structure.

Also, it is a good practice to use the strictures: 

use warnings;
use strict;

[download]

Replies are listed 'Best First'.
Re^2: How to extract a row or column of two-dimensional hash
by PerlKitten (Novice) on Jan 11, 2008 at 21:01 UTC
    Toolic, I had already read the link you provided (and I am using #strict in my code), but didn't find what I needed. Let me try to ask again, using the examples provided in the link (with a few values changes). Please understand also that I've consulted about six Perl books (3 Llama ones) in search of the answer, so I've spent a fair bit of time on this.) I want to count the number of members of each family named jane. I tried the following code:
    #to make this easier to read, HoH is defined below.
    my ($group);
    for $group ("simpsons","jetsons" ) {
    my $janemembers=grep {$_ eq "jane"} values $HoH{$group};
    }
    The error given is that "Type of arg1 to values must be hash (not hash element). What's going wrong??
    %HoH = (
    flintstones => {
    lead => "fred",
    pal => "barney",
    },
    jetsons => {
    lead => "george",
    wife => "jane",
    kid => "jane",
    },
    simpsons => {
    lead => "homer",
    wife => "marge",
    kid => "bart",
    },
    );
[reply]
      The error message "Type of arg1 to values must be hash (not hash element)" is giving you precisely the fix you need.

      $HoH{$group} is a hash element. The keys function you have in front of it wants a hash, not a hash element. Since that hash element is a reference to the actual hash, you must dereference the reference to get to the hash. In this case, wrap %{ ... } around it, as in %{$HoH{$group}}, and put keys in front of that.

      I'm surprised you checked "3 llamas". The llama doesn't talk about references (deliberately, because there's only so much we can cover in a week). You want The Alpaca instead, which covers this topic (and more!).

      -- Randal L. Schwartz, Perl hacker

[reply]
[d/l]
[select]
      When posting code, please use "code" tags, not "br" tags, as described in Writeup Formatting Tips.

      Updated: $HoH{$group} is a reference to a hash. I refactored your code as follows: 

      #!/usr/bin/env perl

use warnings;
use strict;

my %HoH = (
    flintstones => {
                        lead => "fred",
                        pal => "barney",
    },
    jetsons => {
                        lead => "george",
                        wife => "jane",
                        kid => "jane",
    },
    simpsons => {
                        lead => "homer",
                        wife => "marge",
                        kid => "bart",
    },
);

my $total_jane_count = 0;
for my $group ("simpsons" ,"jetsons" ) {    
    my %family_hash = %{ $HoH{$group} };
    for my $name (values %family_hash) {
        if ($name eq 'jane') { $total_jane_count++ }
    }
} 
print "total_jane_count = $total_jane_count\n";

      [download]

      This prints: 

      total_jane_count = 2

      [download]
[reply]
[d/l]
[select]
        Toolic, thank you for the code.
[reply]

In Section Seekers of Perl Wisdom