Hi Chris,
On Sun, 19 Aug 2012 08:49:25 -0500
Chris Stinemetz <perlqu...@gmail.com> wrote:
> Hello List,
>
> I have input data such as far below:
>
> I would like to read the data into an array and modify the 2nd index
> if the 0th and first indices are identical.
> I would like the updated 2nd index to be an average of the 2nd index
> where both occurences of 0th and 1st indices match.
>
> So for example below:
>
> The records that contain 24 1 I would like to average the second
> index 60 and 40
I would suggest two passes. In the first pass you maintain a hash that maps the
tuple
of the 0th and 1st columns into a count-and-sum record:
# Untested
my %counts_and_sums;
foreach my $item (@array_of_arrays)
{
my $key = join("\0", $item->[0], $item->[1]); # Or some other suitable
serialisation method.
$counts_and_sums{$key}{count}++;
$counts_and_sum{$key}{sum} += $item->[2];
}
Then in the second path, you look up the items' keys in the hash, and if
->{count} is greater
than 1 you assign ->{sum} / ->{count} to $item->[2].
Regards,
Shlomi Fish
>
> and print the new value like this:
>
> ... # print input data
> 24 1 50 65
> 24 1 50 65
> ... # print rest of input data
>
>
>
>
> 22 1 60 65
> 22 2 180 90
> 22 3 300 90
> 23 1 0 65
> 23 2 90 65
> 23 3 260 65
> 24 1 60 65
> 24 1 40 65
> 24 2 180 65
> 24 2 160 65
> 24 3 310 65
> 24 3 290 65
> 25 1 0 90
> 25 2 120 65
> 25 3 240 65
> 26 1 60 65
> 26 2 180 65
> 26 3 320 65
> 87 1 355 65
> 87 2 100 65
> 87 3 245 65
> 87 3 180 65
> 88 1 100 65
> 88 2 210 65
> 88 3 310 65
>
> Thank you in advance.
--
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