在PHP中使用数组查找百分位数

问题描述

我有一个像这样的数组

 array(
      45=>5,
      42=>4.9,
      48=>5,
      41=>4.8,
      40=>4.9,
      34=>4.9,
      .....
      )

这里的索引是userid，价值是他的得分.

Here index is userid and value is his score.

现在我想要的是为用户实现百分位数，例如45.48的百分位数将是99，42,40,34的百分位数将是97，而41的百分位数将是94.

Now what i want is to achieve percentile for on user for example percentile of 45,48 would be 99 and 42,40,34 would be 97 and 41 would be 94.

我该如何实现?

推荐答案

1. 基于分数"对数组进行排序，升序
2. 百分位数=(已排序数组中元素的索引)* 100/(数组中元素总数)

示例:

<?php
$array = array(
      45=>5,
      42=>4.9,
      48=>5,
      41=>4.8,
      40=>4.9,
      34=>4.9,
      );

print("Unsorted array:<br/>");
print_r($array);
arsort($array);
print("<br/>");
print("Sorted array:<br/>");
print_r($array);
print("<br/>");

$i=0;
$total = count($array);
$percentiles = array();
$previousValue = -1;
$previousPercentile = -1;
foreach ($array as $key => $value) {
    echo "\$array[$key] => $value";
    if ($previousValue == $value) {
    $percentile = $previousPercentile;
    } else {
    $percentile = 99 - $i*100/$total;
    $previousPercentile = $percentile;
    }
    $percentiles[$key] = $percentile;
    $previousValue = $value;
    $i++;
}

print("Percentiles:<br/>");
print_r($percentiles);
print("<br/>");

?>

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