如何从 PHP 中的双精度数组计算第 n 个百分位数?

2022-01-07 00:00:00 statistics math php

我有一个很大的双精度数组，我需要计算数组的第 75 个和第 90 个百分位值.通过函数执行此操作的最有效方法是什么?

I have a large array of doubles and I need to calculate the 75th and 90th percentile values for the array. What's the most efficient way to do this via a function?

推荐答案

统计已经有一段时间了，所以我可以离开这里 - 但这里有一个裂缝.

It's been awhile since statistics, so I could be off here - but here's a crack at it. 

function get_percentile($percentile, $array) {
    sort($array);
    $index = ($percentile/100) * count($array);
    if (floor($index) == $index) {
         $result = ($array[$index-1] + $array[$index])/2;
    }
    else {
        $result = $array[floor($index)];
    }
    return $result;
}

$scores = array(22.3, 32.4, 12.1, 54.6, 76.8, 87.3, 54.6, 45.5, 87.9);

echo get_percentile(75, $scores);
echo get_percentile(90, $scores);

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