how to compute the centroid of the PointCloud2

I am considering how can I compute the centroid of sensor_msgs/PointCloud2, is there a direct way to do this? Because I only find he pcl::CentroidPoint< PointT > Class Template Reference *[link text] (http://docs.pointclouds.org/trunk/classpcl_1_1_centroid_point.html#details) on the website.