Re: Summing repeated counts for items stored in separate file

Here is a really simple solution that will not use too much memory.

use strict;

use vars qw (%data);

open(KEYS, "keys.txt") or die "error: keys.txt $!";
open(VALS, "values.txt") or die "error: values.txt $!";

while (my $key = readline(*KEYS)) {
    my $val = readline(*VALS);
    chomp $key;
    chomp $val;

    print "$key = $val\n";
    unless (exists $data{$key}) {
        $data{$key}{min} = $data{$key}{max} = $data{$key}{total} = $va
+l;
        $data{$key}{count} = 1;
    } else {
        $data{$key}{min} = $val if $data{$key}{min} > $val;
        $data{$key}{max} = $val if $data{$key}{max} < $val;
        $data{$key}{total} += $val;
        $data{$key}{count}++;
    }
}

use Data::Dumper;
print Dumper \%data;
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-- gam3
A picture is worth a thousand words, but takes 200K.

Comment on Re: Summing repeated counts for items stored in separate file Download Code

Replies are listed 'Best First'.
Re^2: Summing repeated counts for items stored in separate file by dmorgo (Pilgrim) on Jul 28, 2007 at 21:10 UTC
Thanks. Nice looking code. Why readline(*KEYS) instead of <KEYS> ?	[reply]
Re^3: Summing repeated counts for items stored in separate file by mjscott2702 (Pilgrim) on Jul 29, 2007 at 23:41 UTC
The readline function is what is used "behind the scenes" to implement the <> operator, and takes a typeglob, hence *KEYS instead of <KEYS>; Keeping track of the min, max, total and count (for average value) may be faster than using the List utilities described earlier, or at least should take less memory, since you only need to keep track of a few values for each key. Although the utilities in question are extremely fast, you might need an array of thousands of values for each key, growing in size as you process the files.	[reply]
Re^4: Summing repeated counts for items stored in separate file by dmorgo (Pilgrim) on Aug 07, 2007 at 01:54 UTC
You said: The readline function is what is used "behind the scenes" to implement the <> operator, and takes a typeglob, hence *KEYS instead of <KEYS>; OK, I follow you, but what's the benefit of using readline instead of simply <>?	[reply]