public function __construct($points, $α, int $λ)
{
$this->α = $α;
$this->λ = $λ;
parent::__construct($points);
// α ∈ ((λ + 1) / n, 1]
if ($α <= ($λ + 1) / $this->n || $α > 1) {
throw new Exception\OutOfBoundsException('Smoothness parameter α must be between ' . ($λ + 1) / $this->n . " and 1; given {$α}");
}
// Number of points considered in the local regression
$this->number_of_points = min(ceil($this->α * $this->n), $this->n);
}