1,查看R中的变量模式（对象的数据类型）mode()
2,因子（factor）, table()可以获取多个因子的交叉表，可以知道每个因子出现的次数
> g<-c("f","m","m","m","f","f","m","f","m","f")
> g<-factor(g)
> a<-factor(c("adult","junvenile","adult","adult","junvenile","adult","adult","junvenile","adult","adult"))
> table(a,g)
g
a f m
adult 3 4
junvenile 2 1
3，数据框
简单对数据框进行查询，可以用attach（detach）和subset（）函数
4，查看R语言内置的数据集
用data()即可查看各种数据集
