3-5 处理缺失值> x <- c(1,NA,2,NA,3)
> is.na(x)
[1] FALSE TRUE FALSE TRUE FALSE
> x[!is.na(x)] #找出不是缺失值
[1] 1 2 3
> x <- c(1,NA,2,NA,3)
> y <- c("a","b",NA,"c",NA)
> z <- complete.cases(x,y) #都不是缺失值的元素
> x[z]
[1] 1
> y[z]
[1] "a"
> library(datasets) #import dat