Performance diagnosis of elite table tennis competition based on rough set theory

The problems of the diagnosis of table tennis technique lie in neglecting the relationships between skills and placements, and arriving isolated conclusions. The article rebuilds the technical performance indicator system through a combined analysis of technical behaviors and ball placements. The technical data of matches (225 competitions) is collected by Data Collection Software. The attribute reduction algorithm of rough sets is applied to get the reduction set of technical data, the result of which shows that the winning factors lie in each player´s individual strength, for instance, Ma Lin and Wang Liqin´s forehand attack, Wang Hao´s backhand, Boll´s middle serve, Ryu Sheng min´s chopping short, and Samsonov´s forehand placement are major ways to get scores; Zhang Yining´s defending, Wang Nan´s creating opportunities by good forehand techniques, Guo Yue´s high quality serve, Tie Yana´s forehand flipping, Fukuhara Ai´s forehand attack, and Li Jiawei´s backhand attack are all winning factors. To sum up, the new indicator system shows the relationship between technical behaviors and placements. The reduction method of rough sets finds minimal sets, which shares the same knowledge with the original data, forms the winning factors of table tennis competitions.