#!/usr/bin/perl -w

use strict;
use Math::Random;

my %shiftSchedule = (
    "first" =>  { "start" => 8.00, "end" => 16.00 },
    "second" => { "start" => 18.00, "end" => 24.00 },
    "third" =>  { "start" => 24.00, "end" =>  8.00 }
);
my $shift = "third";         # shift to monitor
my $inspectionRate = 1 / 2;  # every 1/2 hour
my $drift = 1.5;             # drift to simulate
my $m = 25;                  # samples in control chart setup
my $n = 3;                   # observations per sample
my $target = 100.0;          # quality characteristic target

my $hour;
my $i;
my $j;
my $minute;
my $observation;
my $setupM = $m;

print "timestamp sample observation phase\r\n";

for ($i = 1; $i <= $m; $i++) {
    for ($j = 0; $j < $n; $j++) {
	$observation = $target + random_normal();
	printf "     0:00 %6d     %7.3f setup\r\n", $i, $observation;
    }
}

$m = $shiftSchedule{$shift}{"end"} - $shiftSchedule{$shift}{"start"};
if ($m < 0) {
    $m += 24;
}
$m /= $inspectionRate;
for ($i = 1; $i <= $m; $i++) {
    $hour = int($i * $inspectionRate + $shiftSchedule{$shift}{"start"});
    if ($hour >= 24) {
	$hour -= 24;
    }
    $minute = ($i & 0x1) ? (60 * $inspectionRate) : 0;
    for ($j = 0; $j < $n; $j++) {
	$observation = $target + random_normal();
	if ($i >= (0.25 * $m)) {
	    if ($i < (0.75 * $m)) {
		$observation += ($drift / (0.5 * $m)) * ($i - (0.25 * $m));
	    } else {
		$observation += $drift;
	    }
	}
	printf "    %2d:%02d %6d     %7.3f monitoring\r\n", $hour, $minute, $setupM + $i, $observation;
    }
}