具有概率的随机函数

Question

我有一个包含以下数据的数组：

(
    [Blue] => 15.3
    [Red] => 64.7
    [Green] => 20.0
)

蓝色被选中的概率为15.3%，红色被选中的概率为64.7%，绿色为20%强>机会。

我需要创建一个函数来随机选择其中一种颜色，同时还要考虑概率。

Answer 1

我很确定这个函数应该可以为您解决问题，如果需要，您可以将其调整为小数点后的点：

编辑：进行了一些实际测试并稍微修改了代码（以及添加大量输出以供您查看发生了什么：

<?php 
function chance($input=array())
{
    echo 'The Max Value can be: '.(array_sum($input)*10).'<br>';
    $number=rand(0,array_sum($input)*10);
    echo 'Checking for: '.$number.'<br>';
    $starter=0;
    foreach($input as $key => $val)
    {
        $starter+=$val*10;
        echo 'Current value being tested against is: '.$starter.' which is '.$key.'<br>';
        if($number<=$starter)
        {
            $ret=$key;
            break;
        }

    }

    return $ret;
}

$array=array('Blue' => 15.3, 'Red' => 64.7, 'Green' => 20.0);

for($i=0;$i<10;$i++)
{
    echo chance($array).'<br><br>';
}
?>

示例输出：

The Max Value can be: 1000
Checking for: 355
Current value being tested against is: 153 which is Blue
Current value being tested against is: 800 which is Red
Red

The Max Value can be: 1000
Checking for: 63
Current value being tested against is: 153 which is Blue
Blue

The Max Value can be: 1000
Checking for: 692
Current value being tested against is: 153 which is Blue
Current value being tested against is: 800 which is Red
Red

The Max Value can be: 1000
Checking for: 803
Current value being tested against is: 153 which is Blue
Current value being tested against is: 800 which is Red
Current value being tested against is: 1000 which is Green
Green

The Max Value can be: 1000
Checking for: 360
Current value being tested against is: 153 which is Blue
Current value being tested against is: 800 which is Red
Red

The Max Value can be: 1000
Checking for: 174
Current value being tested against is: 153 which is Blue
Current value being tested against is: 800 which is Red
Red

The Max Value can be: 1000
Checking for: 117
Current value being tested against is: 153 which is Blue
Blue

The Max Value can be: 1000
Checking for: 769
Current value being tested against is: 153 which is Blue
Current value being tested against is: 800 which is Red
Red

The Max Value can be: 1000
Checking for: 462
Current value being tested against is: 153 which is Blue
Current value being tested against is: 800 which is Red
Red

The Max Value can be: 1000
Checking for: 418
Current value being tested against is: 153 which is Blue
Current value being tested against is: 800 which is Red
Red

Answer 2

使用mt_rand，您可以选择最小值和最大值。 例如，您使用 0 到 100。

$randomValue = (mt_rand ( 0 , 1000 ) / 10)

然后，只需选择适合您的百分比的违规行为，如下所示：

if($randomValue <= 15.3) { $pick = 'Blue';}
elseif($randomValue <= 64.7) { $pick = 'Red';}
else { $pick = 'Green';}

使用您的数组，您可以在函数中轻松实现这一点。 只需按值对数组进行排序，然后适当处理。

function getRandomColor($colorsWithProbability) {
  sort($colorsWithProbability);
  $last = '';

  foreach($colorsWithProbability as $color => $probability) {
    $last = $color;
    if($randval <= $probability) {
      return $color;
    }
  }
  return $last;
}