Biased.php
| 1 | <?php |
| 2 | |
| 3 | namespace Faker\Provider; |
| 4 | |
| 5 | class Biased extends Base |
| 6 | { |
| 7 | /** |
| 8 | * Returns a biased integer between $min and $max (both inclusive). |
| 9 | * The distribution depends on $function. |
| 10 | * |
| 11 | * The algorithm creates two doubles, x ∈ [0, 1], y ∈ [0, 1) and checks whether the |
| 12 | * return value of $function for x is greater than or equal to y. If this is |
| 13 | * the case the number is accepted and x is mapped to the appropriate integer |
| 14 | * between $min and $max. Otherwise two new doubles are created until the pair |
| 15 | * is accepted. |
| 16 | * |
| 17 | * @param integer $min Minimum value of the generated integers. |
| 18 | * @param integer $max Maximum value of the generated integers. |
| 19 | * @param callable $function A function mapping x ∈ [0, 1] onto a double ∈ [0, 1] |
| 20 | * @return integer An integer between $min and $max. |
| 21 | */ |
| 22 | public function biasedNumberBetween($min = 0, $max = 100, $function = 'sqrt') |
| 23 | { |
| 24 | do { |
| 25 | $x = mt_rand() / mt_getrandmax(); |
| 26 | $y = mt_rand() / (mt_getrandmax() + 1); |
| 27 | } while (call_user_func($function, $x) < $y); |
| 28 | |
| 29 | return (int) floor($x * ($max - $min + 1) + $min); |
| 30 | } |
| 31 | |
| 32 | /** |
| 33 | * 'unbiased' creates an unbiased distribution by giving |
| 34 | * each value the same value of one. |
| 35 | * |
| 36 | * @return integer |
| 37 | */ |
| 38 | protected static function unbiased() |
| 39 | { |
| 40 | return 1; |
| 41 | } |
| 42 | |
| 43 | /** |
| 44 | * 'linearLow' favors lower numbers. The probability decreases |
| 45 | * in a linear fashion. |
| 46 | * |
| 47 | * @return integer |
| 48 | */ |
| 49 | protected static function linearLow($x) |
| 50 | { |
| 51 | return 1 - $x; |
| 52 | } |
| 53 | |
| 54 | /** |
| 55 | * 'linearHigh' favors higher numbers. The probability increases |
| 56 | * in a linear fashion. |
| 57 | * |
| 58 | * @return integer |
| 59 | */ |
| 60 | protected static function linearHigh($x) |
| 61 | { |
| 62 | return $x; |
| 63 | } |
| 64 | } |
| 65 |