MCordingley\Regression\Algorithm\GradientDescent\Gradient\Logistic::cost PHP Метод

    public function cost(array $coefficients, array $features, float $outcome) : float
    {
        $predicted = $this->predicted($coefficients, $features);
        return -$outcome * log($predicted) - (1.0 - $outcome) * log(1.0 - $predicted);
    }

 public function testCost()
 {
     $gradient = new Logistic();
     static::assertEquals(-3.8730719889570246, $gradient->cost([1.0], [2.0], 3.0));
 }