@STATE_LOOKUP = (
   undef,      # There's no state 0
   'Maine',
   'Hawaii',
   'Canada',
   'New York',
   ...
);

my $data;

open(FILE, ...) or die(...);

while (defined($line = <FILE>)) {
   my ($state_id, $date) = get_fields($line);
   my $date_n = convert_date_to_number($date);
   $data->[$state_id]->{$date}++;
}

close(FILE);

{ # Sample output.
   my ($state_id, $date_n);
   for ($state_id=1; $state_id<=50; $state_id++) {
      my $state = $STATE_LOOKUP[$state_id];
      foreach $date_n (sort { $a <=> $b } keys %{$data->[$state]}) {
         my $date = convert_date_to_string($date_n);
         my $num_tornadoes = $data->[$state]{$date_n};
         printf("State %s had %d tornado(es) on %s\n",
            $state,
            $num_tornadoes,
            $date,
         ) if $num_tornadoes;
      }
   }
}

[download]

get_fields depends on the format of your data.

Look into the Time modules for help implementing convert_date_to_number.

Others will probably use a hash for states without thinking, but an array would be more efficient and just as powerful (assuming you have reports for many states).

In reply to Re: Help with calculating stats from a flat-file database by ikegami
in thread Help with calculating stats from a flat-file database by nadocane

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