课后习题：
x1 = c(13,15,16,16,19,20,20,21,22,22,25,25,25,25,30,33,33,35,35,35,35,36,40,45,46,52,70); print(round(mean(x1))); #平均值 print(median(x1,na.rm=TRUE)); #中值
R语言数据分析、展现与实例 (第一周)
原文：http://www.cnblogs.com/fm365/p/4631512.html
