CosineSimilarity

CosineSimilarity measures a cosine similarity between two vectors.

USAGE

require_once 'CosineSimilarity.php';

sample data: word => term frequency

$v1 = array('php' => 5, 'web' => 2,  'google' => 1);
$v2 = array('php' => 0, 'web' => 5,  'google' => 10);
$v3 = array('php' => 0, 'web' => 10, 'google' => 5);
$v4 = array('php' => 5, 'web' => 2,  'google' => 1);

calculate

$cs = new CosineSimilarity();

$result1 = $cs->similarity($v1,$v2); // similarity of 1 and 2
$result2 = $cs->similarity($v1,$v3); // similarity of 1 and 3
$result3 = $cs->similarity($v1,$v4); // similarity of 1 and 4

var_dump($result1); // #=> float(0.32659863237109)
var_dump($result2); // #=> float(0.40824829046386)
var_dump($result3); // #=> float(1)

NOTES

CosineSimilarity::_absVector(array $vec) is faster than the following logic:

return sqrt(array_sum(array_map(function($value) { return $value * $value; }, $vec)));