DiceSimilarity extension for php-nlp-tools

DiceSimilarity.php

<?php
namespace App\Utilities;


/**
 * http://en.wikipedia.org/wiki/Sørensen–Dice_coefficient
 */

class DiceSimilarity
{


   /**
    * The similarity returned by this algorithm is a number between 0,1
    */

    public function similarity($A, $B)
    {

        $a = array_fill_keys($A,1);
        $b = array_fill_keys($B,1);

        $intersect = count(array_intersect_key($a,$b));
        $a_count = count($a);
        $b_count = count($b);

        return (2*$intersect)/($a_count + $b_count);
    }

    public function dist(&$A, &$B)
    {
        return 1-$this->similarity($A,$B);
    }
}