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April 25, 2023 23:53
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Get distribution-based random element in PHP
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| <?php | |
| function randomWithDistribution(array $elements) { | |
| if(array_sum($elements) !== 100) { | |
| throw new \Exception('randomWithDistribution: sum of probabilities must be 100'); | |
| } | |
| $random = rand(1, 100); | |
| $tot = 0; | |
| foreach($elements as $id => $weight) { | |
| $tot += $weight; | |
| if($random <= $tot) { | |
| return $id; | |
| } | |
| } | |
| } | |
| /** | |
| * Test | |
| */ | |
| //initialize the table of results | |
| $rounds = ['a'=>0, 'b'=>0, 'c'=>0]; | |
| //populate the results by applying the function | |
| for($i=0; $i<10000; $i++) { | |
| $v = randomWithDistribution(['a'=>15, 'b'=>70, 'c'=>15]); | |
| $rounds[$v]++; | |
| } | |
| //render the results | |
| echo '<pre>'; | |
| foreach($rounds as $id => $count) { | |
| $percent = $count / 100 * count($rounds); | |
| echo str_pad($id, 2, '000', STR_PAD_LEFT), '. ', str_repeat('-', $percent), $count, ' .. ', $percent, '%<br />'; | |
| } | |
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