PHP Conference Nagoya 2025

    stats_stat_percentile

    (PECL stats >= 1.0.0)

    stats_stat_percentile — Returns the percentile value

    Descrição

    stats_stat_percentile(array $arr, float $perc): float

    Returns the perc-th percentile value of the array arr.

    Parâmetros

    arr

    The input array

    perc

    The percentile

    Valor Retornado

    Returns the percentile values of the input array.

    Melhore Esta Página

    Aprenda Como Melhorar Esta Página • Envie uma Solicitação de Modificação • Reporte um Problema
    ＋adicione uma nota

    Notas Enviadas por Usuários (em inglês) 2 notes

    up
    7
    aboulang2002 at yahoo dot com
    15 years ago
    If you are looking to infer the percentile from a z-score, you can use this function.
    It's far from precise but does the job on most circumstances.
    The error function ( erf() )is based on the approximation on wikipedia:
    http://en.wikipedia.org/wiki/Error_function

    <?php
    function erf($x)
    {
    $pi = 3.1415927;
    $a = (8*($pi - 3))/(3*$pi*(4 - $pi));
    $x2 = $x * $x;

    $ax2 = $a * $x2;
    $num = (4/$pi) + $ax2;
    $denom = 1 + $ax2;

    $inner = (-$x2)*$num/$denom;
    $erf2 = 1 - exp($inner);

    return     sqrt($erf2);
    }

    function     cdf($n)
    {
    if(    $n < 0)
    {
    return (    1 - erf($n / sqrt(2)))/2;
    }
    else
    {
    return (    1 + erf($n / sqrt(2)))/2;
    }
    }

    // EXAMPLE
    $sample = 90;
    $avg = 75;
    $stddev = 12;

    $zscore = ($sample - $avg) / $stddev;
    print     'Percentile: ' . cdf($zscore) * 100 . "\n";
    ?>

    Where $n is the z-score

    The function cdf() returns the approximed cumulative standard normal distribution ([0..1])



    [EDIT BY danbrown AT php DOT net: Contains a bugfix provided by (Ed) on 24-FEB-2010 which fixes the definition of $a in erf() with the note that it is "out by a factor of -1" in the original code.]
    up
    4
    yuvaraj dot v at gmail dot com
    16 years ago
    I have looked at the code available in the Math package for percentile. I compared the result obtained with percentile from Excel and found that it doesnt match. So i wrote my own percentile function and verified the result with the Excel's percentile.

    For those of you who need the percentile calculation of Excel in php..

    <?php
    function mypercentile($data,$percentile){
    if(     0 < $percentile && $percentile < 1 ) {
    $p = $percentile;
    }else if(     1 < $percentile && $percentile <= 100 ) {
    $p = $percentile * .01;
    }else {
    return     "";
    }
    $count = count($data);
    $allindex = ($count-1)*$p;
    $intvalindex = intval($allindex);
    $floatval = $allindex - $intvalindex;
    sort($data);
    if(!    is_float($floatval)){
    $result = $data[$intvalindex];
    }else {
    if(    $count > $intvalindex+1)
    $result = $floatval*($data[$intvalindex+1] - $data[$intvalindex]) + $data[$intvalindex];
    else
    $result = $data[$intvalindex];
    }
    return     $result;
    }
    ?>

    The above code may not be elegant.. but it solves my problem..

    yuvaraj
    ＋adicione uma nota
    To Top