#!/usr/bin/perl

# interval_sum.pl - read in a file of {time value} entries and
# print out the sum every interval
#
# Usage: interval_sum.pl [summing_interval_in_seconds] [starting_second] < file
#
# Michele C. Weigle, mweigle@cs.odu.edu
# Old Dominion University, November 2006

$interval = 1;
$start = 0;

if ($#ARGV == 0) {
  $interval = $ARGV[0];  # summing interval in seconds
  $start = 0;
}
elsif ($#ARGV == 1) {
  $interval = $ARGV[0];
  $start = $ARGV[1];
}

$sum = 0;
$end = $start + $interval;
while (<STDIN>) {
  ($time, $value) = split (" ", $_);
  if ($time < $end) {
    $sum += $value;
  }
  else {
    # time to print out last interval's sum
    while ($time >= $end) {
      printf ("%-.3f %-.3f %lf\n", $start, $end, $sum);
      $start += $interval;
      $end += $interval;
      $sum = 0;
    }
    $sum = $value;
  }
}
# print the final interval's sum
printf ("%-.3f %-.3f %lf\n", $start, $end, $sum);