Weigthed Moving Average (WMA)

<?php
$periode=isset($_GET['period'])?$_GET['period']:3;
$data=array(
  array('2201','1618'),
  array('2202','1625'),
  array('2203','1643'),
  array('2204','1661'),
  array('2205','1678'),
  array('2206','1740'),
  array('2207','1746'),
  array('2208','1749'),
  array('2209','1757'),
  array('2210','1793'),
  array('2211','1810'),
  array('2212','1865'),
);
?>
<html>
<head>
<title>Weighted Metode Moving Average</title>
<style>
td,th {padding:5px;border: solid 1px #333;}
</style>
</head>
<body>
<table>
<caption>Weighted Metode Moving Average (period= <select name='period' onChange='ubah(this.value);'>
<?php
for($i=1;$i<10;$i++){
echo "<option value='{$i}'".($i==$periode?' selected':'').">{$i}</option>";
}
?>
</select>)</caption>
<tr><th>bulan</th><th>penjualan(y)</th><th>prediksi(x)</th>
<th>MAPE |(y-x)/y|</th>
<th>MAD |(y-x)|</th>
<th>MSE (y-x)<sup>2</th>
</tr>
<?php
$prediksi=$mape=$mad=array();
$panjang_data=count($data);
for($i=$periode;$i<$panjang_data;$i++){
  $pembagi=0;
  $jml=0;
  for($j=$i-$periode;$j<$i;$j++){
    $jml+=$data[$j][1]*($j-($i-$periode)+1);
    $pembagi+=($j-($i-$periode)+1);
  }
  $prediksi[$data[$i][0]]=$jml/$pembagi;
  $mape[$data[$i][0]]=abs(($prediksi[$data[$i][0]]-$data[$i][1])/$prediksi[$data[$i][0]]);
  $mad[$data[$i][0]]=abs($prediksi[$data[$i][0]]-$data[$i][1]);
  $mse[$data[$i][0]]=pow($mad[$data[$i][0]],2);
}
foreach($data as $k=>$v){
  echo "<tr><td>{$v[0]}</td><td>{$v[1]}</td>"
      ."<td>".($k<$periode?"-":round($prediksi[$v[0]],4))."</td>"
      ."<td>".($k<$periode?"-":round($mape[$v[0]],4))."</td>"
      ."<td>".($k<$periode?"-":round($mad[$v[0]],4))."</td>"
      ."<td>".($k<$periode?"-":round($mse[$v[0]],4))."</td>"
      ."</tr>";
}
$total_mape=round(array_sum($mape),4);
$total_mad =round(array_sum($mad),4);
$total_mse =round(array_sum($mse),4);

$jml_mape=count($mape);
$jml_mad=count($mad);
$jml_mse=count($mse);

$hasil_mape=round($total_mape/$jml_mape*100,4);
$hasil_mad =round($total_mad/$jml_mad,4);
$hasil_mse =round($total_mse/$jml_mse,4);

echo "<tr><th colspan='3'>Total</th><th>{$total_mape}</th><th>{$total_mad}</th><th>{$total_mse}</th></tr>";
echo "<tr><th colspan='3'>Jumlah Data</th><th>{$jml_mape}</th><th>{$jml_mad}</th><th>{$jml_mse}</th></tr>";
echo "<tr><th colspan='3'>Hasil</th><th>{$hasil_mape} %</th><th>{$hasil_mad}</th><th>{$hasil_mse}</th></tr>";
?>
</table>
<p>
<b>MAPE</b>  = <i>Mean Absolute Percent Error</i><br />
<b>MAD</b>  = <i>Mean Absolute Deviation</i><br />
<b>MSE</b>  = <i>Mean Squared Error</i>
</p>
<script>
function ubah(nilai){
  location.href='?period='+nilai;
}
</script>
</body>
</html>