#!/usr/bin/perl -w

$size = 40;

# Generate array of random values and calculate sample mean
$m = 0;
for ($i=0; $i<$size; $i++) {
#  $t = 0;   # Use this for pure random
#  $t = 4 * sin( $i/2 );  # use this for periodic plus random
  $t = (2*$i*$i - 5*$i + 3)/($size*$size);  # use this for quadratic plus random
  $t += -1 + rand 2;
  $x[$i] = $t;
  $m += $t;
  print "$t\n";
}
$m /= $size;

print "----------\n";

# calculate sample covariances
for ($h=0; $h<$size-10; $h++) {
  $sum = 0;
  for ($t=0; $t<$size-$h; $t++) {
    $sum += ($x[$t+$h] - $m)*($x[$t] - $m);
  }
  $sum /= $size;
  print "$sum\n";
}