Well, I recommend doing some reading ! His/Her grace, ikegami (Archbishop), used a hash (%flushes) to collect the results. Hashes are a wonderful thing, and worth getting to grips with.

However, his/her grace did use a "two dimensional" hash, which is rather throwing you into the murkier part of the deep end.

So, let's simplify this, a bit. Your first requirement was to count the number of whatever they were, on a monthly basis. The regular expression extracted the month name and year from the date into the string $month, for example 'Aug-2008'. You could use the hash %total_counts to count the totals for each month, thus: $total_counts{$month}++.

To extract the totals for each month you could: 

  while (my ($month, $total) = each(%total_counts)) {
    print "$month: $total\m" ;
  } ;

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where each(%total_counts) walks the hash and returns key and value pairs -- but in some apparently random order. You could: 
  foreach my $month (sort keys %total_counts) {
    print "$month: $total_counts{$month}\n" ;
  } ;

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where keys %total_counts returns a list of all of the keys in %total_counts (in some apparently random order), which is then sorted alphabetically -- so the output is the counts so sorted. You probably want: 
  foreach my $month (sort_months(keys %total_counts)) {
  ....

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where the subroutine sort_months() is left as an exercise -- taking in a list of month strings and returning a list in the required order.

Your second requirement was to count for each user, on a monthly basis. So you want a hash, say %user_counts, with an entry for each user: $user_counts{$user}. Each entry needs to be a separate count for each month... now things are getting tricky. A hash entry is a single scalar value; you cannot have hash entries which are arrays or hashes. However, you can have scalars which are references to arrays or hashes. So, where the entries in %total_counts are simple (numeric) scalars, the entries in %user_counts are references to hashes, each hash being similar to %total_counts -- that is, the key value is a month string (eg 'Aug-2008') and the value is the count for that month. The short hand in Perl to refer to a count value in this structure is $user_counts{$user}{$month} -- meaning: (a) get entry in %user_counts whose key is $user, (b) that entry refers to a hash, get the entry in that hash whose key is $month.

To extract the per user data is: 

  foreach my $user (sort keys %user_counts) {
    my $r_counts = $user_counts{$user} ;
    print "$user:\n" ;
    foreach my $month (sort_months(keys %$r_counts)) {
      my $count = $user_counts{$user}{$month} ;
      print "  $month $count\n" ;
    } ;
  } ;

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where $r_counts is a reference to a hash that gives the count per month. keys %$r_counts returns the keys in "the hash" ('%') "refered to by the scalar $r_counts".

Depending in how you want the results organised, you may want to change how it's printed or even how it's stored -- the essence is that you can extract the keys using keys and then use them in whatever order you want to look up the data you have collected.

His/Her Grace chose the $month as the primary key, and chose to hold the totals count as the conventional user 'TOTAL' -- you can make up your own mind which order the keys should be in, and whether you think there's an real chance of a real user called 'TOTAL'.

In reply to Re^3: Extracting and counting string occurences by gone2015
in thread Extracting and counting string occurences by joec_

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