Fig. 8
From: SKDStream: a dynamic clustering algorithm on time-decaying data stream
The instance of deleting leaf nodes in 2D SKDTree. On the left side of figure 8 is an SKDTree corresponding to the data space on the right. In the SKDTree, non-leaf nodes are represented as hollow circles, sub-leaf nodes as orange squares, and leaf nodes as purple triangles. In the right side, the gray shaded part are in line with non-leaf node C