table()
参数类型one or more objects which can be interpreted as factors (including character strings)， or a list (or data frame) whose components can be so interpreted. (For as.table， arguments passed to specific methods for as.data.frame， unused.)
我们一般使用将参数转化为用unlist（）列表转化为向量类型
返回值为table类型，一种类似于字典的类型
