r - for循环R中的样本

Question

我想从 MU、MG、PU、PG 中采样 70 次以创建一个矩阵(ncol=4，nrow=70)例如

sample(c("MU","MG","PU","PG"), 4,F)
sample(c("MU","MG","PU","PG"), 4,F)
sample(c("MU","MG","PU","PG"), 4,F)
sample(c("MU","MG","PU","PG"), 4,F)
sample(c("MU","MG","PU","PG"), 4,F)
#etc

到目前为止，我有:matrix(sample(c("MU","MG","PU","PG"), 70*4,F), nrow = 70, byrow = TRUE) 这是不对的，因为行可能超过仅举 MU、MG、PU、PG 中的每一个实例。我可以使用 for 循环或更简单的方法来做到这一点吗？

Answer 1

replicate 函数可能正是您要寻找的。我只会重复 10 次，以免溢出屏幕。

> sample(c("MU","MG","PU","PG"), 4,F)
[1] "MG" "MU" "PU" "PG"
> replicate(10, sample(c("MU","MG","PU","PG"), 4,F))
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "MG" "PG" "MU" "MU" "PU" "MG" "PU" "MG" "MG" "MU" 
[2,] "PU" "MG" "PU" "PU" "MU" "MU" "MU" "PG" "MU" "PG" 
[3,] "MU" "PU" "MG" "PG" "MG" "PG" "MG" "MU" "PG" "MG" 
[4,] "PG" "MU" "PG" "MG" "PG" "PU" "PG" "PU" "PU" "PU" 
> # Output is transposed from how we would want it so we'll just transpose it back
> t(replicate(10, sample(c("MU","MG","PU","PG"), 4,F)))
      [,1] [,2] [,3] [,4]
 [1,] "MG" "PU" "PG" "MU"
 [2,] "PU" "MG" "MU" "PG"
 [3,] "MG" "MU" "PU" "PG"
 [4,] "PU" "PG" "MU" "MG"
 [5,] "MG" "PU" "PG" "MU"
 [6,] "PU" "PG" "MU" "MG"
 [7,] "PG" "MG" "PU" "MU"
 [8,] "MU" "PU" "MG" "PG"
 [9,] "PG" "MU" "PU" "MG"
[10,] "MU" "MG" "PG" "PU"