R语言中sample函数

 

1、随机抽样

> a <- 1:10
> sample(a,5)
[1]  9  4  5 10  6
> sample(a,5,replace = T)
[1] 10  7  5  3  4
> sample(a,5,replace = T)   ## 有放回抽样
[1] 5 9 5 1 3

 

> b <- LETTERS[1:10]
> b
 [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J"
> sample(b,5)
[1] "F" "D" "J" "G" "A"
> sample(b,5)
[1] "G" "I" "H" "E" "D"
> sample(b,5,replace = T)
[1] "F" "G" "C" "I" "H"
> sample(b,5,replace = T)
[1] "I" "G" "G" "I" "A"

 

2、随机抽一万行

> data <- read.table("outcome.map")
> dim(data)
[1] 46827     4
> data2 <- data[sample(1:nrow(data), 10000),]
> dim(data2)
[1] 10000     4