/** * Computes the population standard deviation for the numbers * in this list * @return string */ public function stdDev() { Number::setScale(static::NUMERIC_FUNCTIONS_SCALE); $mean = $this->average(); $squares = new static(); foreach ($this->_Arr as $num) { $squares->add(Number::pow(Number::sub(\strval($num), $mean), '2')); } return Number::sqrt($squares->average()); }
public function testSqrt() { $n = '121'; $exp = '11'; $this->assertEquals($exp, Number::sqrt($n)); }