一、函数介绍
nchar takes a character vector as an argument and returns a vector whose elements contain the sizes of the corresponding elements of x.
nchar的参数是一个字符向量，返回对应位置上字符串的长度
nzchar is a fast way to find out if elements of a character vector are non-empty strings.
二、用法
nchar(x, type = "chars", allowNA = FALSE, keepNA = NA)
nzchar(x, keepNA = FALSE)
三、例子
