src/Maths/Algebra/Matrix.php
public function nextX()
    {
        if ($this->nextXExists()) {
            $this->seekX($this->keyX()+1);
        } else {
            $this->x = null;
        }
        return $this;
    }
public function nextX()
    {
        if ($this->nextXExists()) {
            $this->seekX($this->keyX()+1);
        } else {
            $this->x = null;
        }
        return $this;
    }
Seek to current `x` plus 1

@return  $this