r - 如何移动R中矩阵的每一行

Question

我有一个这种形式的矩阵:

a b c
d e 0
f 0 0

我想把它变成这样的:

a b c
0 d e
0 0 f

移动模式是这样的:

shift by 0 for row 1
shift by 1 for row 2
shift by 2 for row 3
...
shift by n-1 for row n

当然，这可以用 for 循环来完成。我想知道是否有更好的方法吗？

Answer 1

假设您的示例具有代表性，即您始终具有字母和零的三角形结构:

mat <- structure(c("a", "d", "f", "b", "e", "0", "c", "0", "0"), 
                 .Dim = c(3L, 3L), .Dimnames = list(NULL, NULL))
res <- matrix(0, nrow(mat), ncol(mat))
res[lower.tri(res, diag=TRUE)] <- t(mat)[t(mat)!="0"]
t(res)
#     [,1] [,2] [,3]
# [1,] "a"  "b"  "c" 
# [2,] "0"  "d"  "e" 
# [3,] "0"  "0"  "f"