从置换向量生成置换矩阵

Question

假设我有一个置换向量（行置换）

x <- c(1,2,3,4,7,8,5,6,9,10) # I exchanged 7 with 5 and 8 with 6.

R中是否有任何函数可以从置换向量生成相应的置换矩阵？如果是这样，请举个例子。

Answer 1

我相信这可以通过重新排序单位矩阵的行来完成：

x <- c(1,2,3,4,7,8,5,6,9,10)
diag(length(x))[x,]
#       [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
#  [1,]    1    0    0    0    0    0    0    0    0     0
#  [2,]    0    1    0    0    0    0    0    0    0     0
#  [3,]    0    0    1    0    0    0    0    0    0     0
#  [4,]    0    0    0    1    0    0    0    0    0     0
#  [5,]    0    0    0    0    0    0    1    0    0     0
#  [6,]    0    0    0    0    0    0    0    1    0     0
#  [7,]    0    0    0    0    1    0    0    0    0     0
#  [8,]    0    0    0    0    0    1    0    0    0     0
#  [9,]    0    0    0    0    0    0    0    0    1     0
# [10,]    0    0    0    0    0    0    0    0    0     1

Answer 2

也可以使用sparseMatrix

完成此操作

library(Matrix)
m1 <- sparseMatrix(seq_along(v1), v1, x=1)

我们可以使用matrix

将其强制转移到as.matrix

as.matrix(m1)

数据

v1 <- c(1,2,3,4,7,8,5,6,9,10)