Perl: Generating Arrays inside a Complex Hash

Question

In the quest to make my data more accessible, I want to store my tabulated data in a complex hash. I am trying to grow a \'HoHoHoA\' as the script loops over my data. As per

Answer 1

This should do it for you.

#!/usr/bin/perl

use strict;
use warnings;

use List::Util qw/sum/;
sub avg { sum(@_) / @_ }

my $fileName = shift;

open my $fh, "<", $fileName
    or die "Unable to open $fileName: $!\n";

my %monthData;

chomp(my @headers = split /\t+/, <$fh>);

while (<$fh>) {
    chomp;
    my %rec;
    @rec{@headers} = split /\t+/;
    my ($hour) = split /:/, $rec{TIME}, 2;

    for my $key (grep { not /^(DATE|TIME)$/ } keys %rec) {
        push @{ $monthData{$key}{$rec{DATE}}{$hour} }, $rec{$key};
    }
}

for my $column (keys %monthData) {
    for my $date (keys %{ $monthData{$column} }) {
        for my $hour (keys %{ $monthData{$column}{$date} }) {
            my $avg = avg @{ $monthData{$column}{$date}{$hour} };
            print "average of $column for $date $hour is $avg\n";
        }
    }
}

Things to pay attention to:

• strict and warnings pragmas
• List::Util module to get the sum function
• putting an array in scalar context to get the number of items in the array (in the avg function)
• the safer three argument version of open
• the lexical filehandle (rather than the old bareword style filehandle)
• reading the headers first outside the loop to avoid having to have special logic inside it
• using a hash slice to get the file data into a structured record
• avoiding splitting the time more than necessary with the third argument to split
• avoiding useless variables by only specifying the variable we want to catch in the list assignment
• using grep to prevent the DATE and TIME keys from being put in %monthData
• the nested for loops each dealing with a level in the hash