MathPHP\Functions\Map\Single::multiply PHP Метод

    public static function multiply(array $xs, $k) : array
    {
        return array_map(function ($x) use($k) {
            return $x * $k;
        }, $xs);
    }

 /**
  * Evaluate for x
  * Use the smoothness parameter α to determine the subset of data to consider for
  * local regression. Perform a weighted least squares regression and evaluate x.
  *
  * @param  number $x
  *
  * @return number
  */
 public function evaluate($x)
 {
     $α = $this->α;
     $λ = $this->λ;
     $n = $this->n;
     // The number of points considered in the local regression
     $Δx = Single::abs(Single::subtract($this->xs, $x));
     $αᵗʰΔx = Average::kthSmallest($Δx, $this->number_of_points - 1);
     $arg = Single::min(Single::divide($Δx, $αᵗʰΔx * max($α, 1)), 1);
     // Kernel function: tricube = (1-arg³)³
     $tricube = Single::cube(Single::multiply(Single::subtract(Single::cube($arg), 1), -1));
     $weights = $tricube;
     // Local Regression Parameters
     $parameters = $this->leastSquares($this->ys, $this->xs, $weights, $λ);
     $X = new VandermondeMatrix([$x], $λ + 1);
     return $X->multiply($parameters)[0][0];
 }