Try this: 
use warnings;
use strict;

use List::Util qw(max min sum);

my %range;
while (<DATA>) {
   my ($time, $value, $error) = split /\s+/;
   push @{ $range{$time} }, $value;
}
foreach my $time (sort keys %range) {
   print "$time ";
   print min( @{ $range{$time} } ) . " ";
   print sum( @{ $range{$time} } )/@{ $range{$time} } . " ";
   print max( @{ $range{$time} } ) . "\n";
}

__DATA__
04/26/04.16:15  3.088   N
04/26/04.16:15  5.994   N
04/26/04.16:15  4.391   N
04/26/04.16:15  3.616   N
04/26/04.16:20  3.997   N
04/26/04.16:20  4.151   N
04/26/04.16:20  3.751   N
04/26/04.16:20  2.887   N
04/26/04.16:25  3.657   N
04/26/04.16:25  4.712   N
04/26/04.16:25  4.346   N
04/26/04.16:30  3.628   N
04/26/04.16:30  5.636   N
04/26/04.16:30  4.593   N

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Here, I have ignored the error code because I did not know what to do in case of conflict between readings.

-Mark

In reply to Re: rearrange data to min, avg, max by kvale
in thread rearrange data to min, avg, max by Earindil

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