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ZScore.php
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ZScore.php
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<?php
namespace ZScore;
class ZScore
{
private $minAverageViews = 50;
private $days;
private $totalViews;
private $totalSquaredViews;
function __construct($days = 0, $totalViews = 0, $totalSquaredViews = 0)
{
if (is_int($days) && ($days >= 0) && is_int($totalViews) && ($totalViews >= 0) && is_int($totalSquaredViews) && ($totalSquaredViews >= 0)) {
$this->days = $days;
$this->totalViews = $totalViews;
$this->totalSquaredViews = $totalSquaredViews;
} else {
throw new Exception("The ZScore Object must get initialized with positive numbers!", 1);
}
}
public function update($views)
{
if (!(is_int($views) && ($views >= 0))) {
throw new Exception(" ZScore::update(): views needs to be a positive number", 1);
}
$this->days++;
$this->totalViews += $views;
$this->totalSquaredViews += pow($views, 2);
}
private function standardDeviation()
{
return sqrt(($this->totalSquaredViews / $this->days) - pow($this->averageViews(), 2));
}
private function averageViews()
{
return $this->totalViews / $this->days;
}
public function calcZScore($views)
{
if (!(is_int($views) && ($views >= 0))) {
throw new Exception("Views needs to be a positive number", 1);
}
if($this->days < 2) {
return 0;
}
if($this->averageViews() < $this->minAverageViews) {
return 0;
}
if($this->standardDeviation() == 0) {
return $views - $this->averageViews();
}
return ($views - $this->averageViews()) / $this->standardDeviation();
}
/**
* Get the value of days
*/
public function getDays()
{
return $this->days;
}
/**
* Get the value of totalViews
*/
public function getTotalViews()
{
return $this->totalViews;
}
/**
* Get the value of totalSquaredViews
*/
public function getTotalSquaredViews()
{
return $this->totalSquaredViews;
}
}