#!/usr/bin/perl -w

use strict;
use Math::Random;

my %shiftSchedule = (
    "first" =>  { "start" =>  6.00, "end" => 14.00 },
    "second" => { "start" => 14.00, "end" => 22.00 },
    "third" =>  { "start" => 22.00, "end" =>  6.00 }
);
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 $target = 100.0;          # quality characteristic target

my $i;
my $observation;
my $setupM = $m;

print "unit observation phase\r\n";

for ($i = 1; $i <= $m; $i++) {
    $observation = $target + random_normal();
    printf "%4d     %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++) {
    $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 "%4d     %7.3f monitoring\r\n", 2 * $setupM + $i, $observation;
}