从数字列表中获取极值 [英] get extremes from list of numbers

问题描述

如果我有一个这样的数字列表:

10,9,8,8,9,7,6,5,4,6,7,8,11,10,12,14,16,20,30,29,28,29,27、25、20、18、15、10、8、5、4、1

我想得到以下数字(根据这个例子):10,4,30,1

是否可以编写一个函数来实现这些极端情况?

这些数字是图表的值，我想获得图表的峰值.

解决方案

我的类似于 jprofitt 的

但是我把它们分成了高峰和低谷，所以我可以用它做更多的事情.

我认为他的循环比我的更干净，但我只是想亲自测试一下.
^{_{不要评判我eeeee}}

这个脚本只是绘制出点并选择峰和谷，并分别给它们绿色和红色.将其视为视觉辅助工具.:P

 $peaks, "valleys" => $valleys, "peak_keys" => $peak_keys, "valley_keys" => $valley_keys);}?><style type="text/css">.容器{位置:绝对；}.观点{位置:绝对；宽度:4px；高度:4px；背景:黑色；}.极端{位置:绝对；顶部:5px；}.extr_low{背景:红色；}.extr_high{背景:绿色；}</风格><?php//阴谋echo "
";foreach($plot as $key => $point){$left = ($key*10);$top = 400 - ($point*10);if(in_array($key, $res['peak_keys']) || in_array($key, $res['valley_keys'])){$extreme = "<div class='extreme'>$point</div>";}别的{$extreme = "";}if(in_array($key, $res['peak_keys'])){$xc = "extr_high";}elseif(in_array($key, $res['valley_keys'])){$xc = "extr_low";}别的{$xc = "";}echo "<div class='point $xc' style='left: ".$left."px; top: ".$top."px;'>$extreme</div>";}echo "</div>";?><表格><tr><th>&nbsp;</th><th>谷</th><th>峰值</th></tr><tr><th>最低</th><td><?php echo min($res['valleys']);?></td><td><?php echo min($res['peaks']);?></td></tr><tr><th>最高</th><td><?php echo max($res['valleys']);?></td><td><?php echo max($res['peaks']);?></td></tr>

If I have a list of numbers like this one:

10,9,8,8,9,7,6,5,4,6,7,8,11,10,12,14,16,20,30,29,28,29,27,25,20,18,15,10,8,5,4,1

I want to get the following numbers (accordint to this example) : 10,4,30,1

Is it possible to write a function which will get these extremes?

These numbers are values of a chart, I want to get peaks of the chart.

解决方案

Mine's similar to jprofitt's

but I divided them into peaks and valleys, so I can do some more stuff with it.

I think his loop is much more cleaner than mine is, but I just wanted to test it out for myself.
^{_{Don't judge meeeeee}}

This script just plots the points out and selects the peaks and valleys and give them green and red respectively. See it as a visual aid. :P

<?php

$plot = array(10,9,8,8,9,7,6,5,4,6,7,8,11,10,12,14,16,20,30,29,28,29,27,25,20,18,15,10,8,5,4,1);

$res = local_extremes($plot);

function local_extremes(array $array){
    $peaks = array();
    $valleys = array();

    $peak_keys = array();
    $valley_keys = array();

    for($i = 0; $i < count($array); $i++){
        $more_than_last = $array[$i] > $array[$i-1];
        $more_than_next = $array[$i] > $array[$i+1];

        $next_is_equal = $array[$i] == $array[$i+1];

        if($next_is_equal) continue;

        if($i == 0){
            if($more_than_next){
                $peaks[] = $array[$i];
                $peak_keys[] = $i;
            }else{
                $valleys[] = $array[$i];
                $valley_keys[] = $i;
            }
        }elseif($i == (count($array)-1)){
            if($more_than_last){
                $peaks[] = $array[$i];
                $peak_keys[] = $i;
            }else{
                $valleys[] = $array[$i];
                $valley_keys[] = $i;
            }
        }else{
            if($more_than_last && $more_than_next){
                $peaks[] = $array[$i];
                $peak_keys[] = $i;
            }elseif(!$more_than_last && !$more_than_next){
                $valleys[] = $array[$i];
                $valley_keys[] = $i;
            }
        }
    }

    return array("peaks" => $peaks, "valleys" => $valleys, "peak_keys" => $peak_keys, "valley_keys" => $valley_keys);
}
?>

<style type="text/css">
    .container{
        position: absolute;
    }

    .point{
        position: absolute;
        width: 4px;
        height: 4px;
        background: black;
    }

    .extreme{
        position: absolute;
        top: 5px;
    }

    .extr_low{
        background: red;
    }

    .extr_high{
        background: green;
    }
</style>

<?php

//Plot
echo "<div class='container'>";
foreach($plot as $key => $point){
    $left = ($key*10);
    $top = 400 - ($point*10);

    if(in_array($key, $res['peak_keys']) || in_array($key, $res['valley_keys'])){
        $extreme = "<div class='extreme'>$point</div>";
    }else{
        $extreme = "";
    }

    if(in_array($key, $res['peak_keys'])){
        $xc = "extr_high";
    }elseif(in_array($key, $res['valley_keys'])){
        $xc = "extr_low";
    }else{
        $xc = "";
    }

    echo "<div class='point $xc' style='left: ".$left."px; top: ".$top."px;'>$extreme</div>";
}
echo "</div>";

?>

<table>
    <tr>
        <th>&nbsp;</th>
        <th>Valley</th>
        <th>Peak</th>
    </tr>
    <tr>
        <th>Lowest</th>

        <td><?php echo min($res['valleys']); ?></td>
        <td><?php echo min($res['peaks']); ?></td>
    </tr>
    <tr>
        <th>Highest</th>
        <td><?php echo max($res['valleys']); ?></td>
        <td><?php echo max($res['peaks']); ?></td>
    </tr>
</table>

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