随机重新排序(洗牌)矩阵的行？

Question

我想随机重新排序矩阵 A 的行以生成另一个新矩阵。如何在 R 中做到这一点？

Answer 1

使用 sample()以(伪)随机顺序生成行索引并使用 [ 重新排列矩阵.

## create a matrix A for illustration
A <- matrix(1:25, ncol = 5)

给予

> A
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    6   11   16   21
[2,]    2    7   12   17   22
[3,]    3    8   13   18   23
[4,]    4    9   14   19   24
[5,]    5   10   15   20   25

接下来，为行生成随机顺序

## generate a random ordering
set.seed(1) ## make reproducible here, but not if generating many random samples
rand <- sample(nrow(A))
rand

这给了

> rand
[1] 2 5 4 3 1

现在用它来重新排序 A

> A
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    6   11   16   21
[2,]    2    7   12   17   22
[3,]    3    8   13   18   23
[4,]    4    9   14   19   24
[5,]    5   10   15   20   25
> A[rand, ]
     [,1] [,2] [,3] [,4] [,5]
[1,]    2    7   12   17   22
[2,]    5   10   15   20   25
[3,]    4    9   14   19   24
[4,]    3    8   13   18   23
[5,]    1    6   11   16   21