Calc() protected method

Calculates position of pie
protected Calc ( )
 /**
  * Calculates reduced radius of pie
  */
 protected function Calc()
 {
     parent::Calc();
     $this->explode_amount = min($this->radius_x - 10, $this->radius_y - 10, max(2, (int) $this->explode_amount));
     $this->radius_y -= $this->explode_amount;
     $this->radius_x -= $this->explode_amount;
 }
 /**
  * Sets up the polar graph details
  */
 protected function Calc()
 {
     // no sorting, no percentage
     $this->sort = false;
     $this->show_label_percent = false;
     parent::Calc();
     $smax = sqrt($this->GetMaxValue());
     $this->radius_factor_x = $this->radius_x / $smax;
     $this->radius_factor_y = $this->radius_y / $smax;
     $this->slice_angle = 2.0 * M_PI / ($this->GetMaxKey() + 1);
 }