MCordingley\LinearAlgebra\Matrix::lower PHP Method

    public function lower(bool $unitriangular) : self
    {
        return $this->map(function (float $element, int $i, int $j) use($unitriangular) {
            if ($unitriangular && $i === $j) {
                return 1;
            }
            return $i < $j ? 0 : $element;
        });
    }

 /**
  * @return Matrix
  */
 public function lower() : Matrix
 {
     return $this->decomposition->lower(true);
 }