src/Maths/Algebra/Matrix.php
public function nextY()
    {
        if ($this->nextYExists()) {
            $this->seekY($this->keyY()+1);
        } else {
            $this->y = null;
        }
        return $this;
    }
public function nextY()
    {
        if ($this->nextYExists()) {
            $this->seekY($this->keyY()+1);
        } else {
            $this->y = null;
        }
        return $this;
    }
Seek to current `y` plus 1

@return  $this