/**
  * Center Y values of the axis 
  *
  * @param awAxis $axis An axis
  * @param float $value The reference value on the axis
  */
 public function setYCenter(awAxis $axis, $value)
 {
     // Check vector angle
     if ($this->line->isHorizontal() === FALSE) {
         trigger_error("setYCenter() can only be used on horizontal axes", E_USER_ERROR);
     }
     $p = $axis->getPointFromValue($value);
     $this->line->setY($p->y, $p->y);
 }
 /**
  * Center Y values of the axis
  *
  * @param awAxis $axis An axis
  * @param float $value The reference value on the axis
  */
 public function setYCenter(awAxis $axis, $value)
 {
     // Check vector angle
     if ($this->line->isHorizontal() === FALSE) {
         awImage::drawError("Class Axis: setYCenter() can only be used on horizontal axes.");
     }
     $p = $axis->getPointFromValue($value);
     $this->line->setY($p->y, $p->y);
 }