Two algorithms of pre-pruning decision tree
两种决策树的事前修剪算法

Pruning decision tree may occur in the process of creating decision tree or after that, the former is called pre-pruning. Every node on decision tree has a corresponding sample set. By analyzing the quantity of sample in the sample set or the purity of it, algorithm PDTBS, viz. pre-pruning decision tree based on support, and algorithm PDTBP, viz. pre-pruning decision tree based on purity were put forward. For pre-pruning, PDTBS prevented the node of a small sample set from extending; PDTBP prevented the node of a high purity sample set from extending. The time complexities of two algorithms were analyzed linear. Experiment results on UCI data show that the two algorithms can pre-prune decision tree to a great extent, while all its accuracy hardly diminishes.