gistfile1.php

<?php
/**
 * なんかよくわからんが PHP 版
 */

$critics = array(
    'Lisa Rose' => array(
        'Lady in the Water' => 2.5, 
        'Snakes on a Plane' => 3.5,
        'Just My Luck' => 3.0,
        'Superman Returns' => 3.5,
        'You, Me and Dupree' => 2.5, 
        'The Night Listener' => 3.0,
    ),
    'Gene Seymour' => array(
        'Lady in the Water' => 3.0,
        'Snakes on a Plane' => 3.5,
        'Just My Luck' => 1.5,
        'Superman Returns' => 5.0,
        'The Night Listener' => 3.0,
        'You, Me and Dupree' => 3.5,
    ), 
    'Michael Phillips' => array(
        'Lady in the Water' => 2.5,
        'Snakes on a Plane' => 3.0,
        'Superman Returns' => 3.5,
        'The Night Listener' => 4.0,
    ),
    'Claudia Puig' => array(
        'Snakes on a Plane' => 3.5,
        'Just My Luck' => 3.0,
        'The Night Listener' => 4.5,
        'Superman Returns' => 4.0,
        'You, Me and Dupree' => 2.5,
    ),
    'Mick LaSalle' => array(
        'Lady in the Water' => 3.0,
        'Snakes on a Plane' => 4.0,
        'Just My Luck' => 2.0,
        'Superman Returns' => 3.0,
        'The Night Listener' => 3.0,
        'You, Me and Dupree' => 2.0,
    ), 
    'Jack Matthews' => array(
        'Lady in the Water' => 3.0,
        'Snakes on a Plane' => 4.0,
        'The Night Listener' => 3.0,
        'Superman Returns' => 5.0,
        'You, Me and Dupree' => 3.5,
    ),
    'Toby' => array(
        'Snakes on a Plane' => 4.5,
        'You, Me and Dupree' => 1.0,
        'Superman Returns' => 4.0,
    ),
);

class Critic
{
    static public function sim_distance($prefs, $person1, $person2){
        if(self::mutual_keys_count($prefs[$person1], $prefs[$person2]) == 0){
            return 0.0;
        }
        $sum_of_squares = 0.0;
        foreach(array_keys($prefs[$person1]) as $k){
            if(isset($prefs[$person2][$k])){
                $sum_of_squares += pow($prefs[$person1][$k] - $prefs[$person2][$k], 2);
            }
        }
        return 1 / (1 + $sum_of_squares);
    }
    static public function sim_pearson($prefs, $person1, $person2){
        $n = self::mutual_keys_count($prefs[$person1], $prefs[$person2]);
        if($n == 0){
            return 0.0;
        }
        $sum1 = array_sum($prefs[$person1]);
        $sum2 = array_sum($prefs[$person2]);
        $sum1sq = self::sum_sq($prefs[$person1]);
        $sum2sq = self::sum_sq($prefs[$person2]);
        $p_sum = 0.0;
        foreach($prefs[$person1] as $k => $v){
            if(isset($prefs[$person2][$k]))
                $p_sum += $v * $prefs[$person2][$k];
        }
        $num = $p_sum - ($sum1 * $sum2 / $n);
        $den = sqrt(($sum1sq - (pow($sum1, 2) / $n)) * ($sum2sq - (pow($sum2, 2) / $n)));
        if($den == 0){
            return 0.0;
        }
        return $num / $den;
    }
    static private function mutual_keys_count($arr1, $arr2){
        $r = 0;
        $keys = array_keys($arr1);
        foreach(array_keys($arr2) as $k){
            if(in_array($k, $keys)) $r++;
        }
        return $r;
    }
    static private function sum_sq($arr){
        $ret = 0.0;
        foreach($arr as $v){
            $ret += pow($v, 2);
        }
        return $ret;
    }
}

/*

$r = Critic::sim_distance($critics, 'Lisa Rose', 'Gene Seymour');
var_dump($r);
$r = Critic::sim_pearson($critics, 'Lisa Rose', 'Gene Seymour');
var_dump($r);

*/