Mathematical averages

arrow has asked for the wisdom of the Perl Monks concerning the following question:

Greetings Perl Monks! I'm working on a rather simple script, but one small part keeps giving me trouble. It is supposed to give an average, but skip nonexistant entries. Maybe I can explain better with the actual code:

for (my $num = $members) {
foreach $month2 (@calendar) {
foreach $name2 (@members) {
if ($hoursWorked{$name2}{$month2} == 0) {
$num--; #this is to protect against false averages, because $members w
+ill usually have a value of 13, but I don't want to count the zero va
+lues because is would result in an incorrect average, (i.e. 24/6 inst
+ead of 24/13 because only 6 people worked)
[download]

$avg{$month2} += $hoursWorked{$name2}{$month2};
}
}
if ($num == 0) {
$avg{$month2} = 0;
}
else {
$avg{$month2} = $avg{$month2}/$num;
}
}
}
[download]

Right now, the problem is that it prints the incorrect averages, like 0 instead of 12. I'm sorry if I couldn't explain well, I barely understand what's going on myself. Anyone have any suggestions?

Just Another Perl Wannabe

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Re: Mathematical averages by dpuu (Chaplain) on Nov 22, 2002 at 22:41 UTC
I think your problem is the initial assignment to $num. Your code is confused: that C<for> statement is not a loop, its just an assignment. But the assignment should be inside the month loop, because you are calculating the average per month. A clearer coding of this might be: `foreach my $month (@calendar) { my $count = 0; my $total = 0; foreach my $value ( grep { $_ != 0 } map { $hoursWorked{$_}{$month} } @members ) { $total += $value; $count ++; } $avg{$month} = $count ? $total/$count : 0; }` [download] --Dave	[reply] [d/l]
Re: Mathematical averages by dws (Chancellor) on Nov 23, 2002 at 01:00 UTC
This line `for (my $num = $members) {` raises a flag. I would expect to see something like `for my $num ( @members ) {` or, if members is a reference to an array, `for my $num ( @$members ) {` Instead, what's there is basically a one-trip loop, which leads me to suspect that this isn't what you intended.	[reply] [d/l] [select]
Re: Mathematical averages by arrow (Friar) on Nov 23, 2002 at 04:00 UTC
Hey, thanks so much dws and dpuu, your answers where just the thing I need. I was surprised at how dpuu's answer worked so well and fast (sorry dws, I just used dpuu's suggesstion first). Anyway, thank you again for saving my butt! Just Another Perl Wannabe	[reply]