/**
* Calculates the amount of entropy in the given data.
*
* @param mixed $data
* @return float
*/
public static function calculateEntropy($data)
{
self::$entropyNumEvents = 0;
self::$entropyTokenFreqs = array();
self::$entropyTokenProbs = array();
self::$entropyValue = 0;
self::$entropyData = $data;
self::$entropyNumEvents = strlen((string) self::$entropyData);
self::entropyFrequencies();
foreach (self::$entropyTokenFreqs as $token => $frequency) {
self::$entropyTokenProbs[$token] = $frequency / self::$entropyNumEvents;
self::$entropyValue += self::$entropyTokenProbs[$token] * log(self::$entropyTokenProbs[$token], 2);
}
self::$entropyValue = -self::$entropyValue;
return self::$entropyValue;
}
