由此
x <- 1:10
block.size <- 3L
我想生成一个长度为3的连续且重叠的块序列，如下所示:
1,2,3
2,3,4
3,4,5
4,5,6
5,6,7
6,7,8
7,8,9
8,9,10
我找到了this nice answer个可以和角色打交道的.
我可以想出一个循环来做这件事，但如果可能的话，我肯定会更喜欢一种更简洁和矢量化的方式.这是我的观点.
block.nums <- length(x)-len+1
blocks <- vector(mode = "list", length = block.nums)
for (i in 1:block.nums) {
blocks[[i]] <- i:(i+block.size-1)
}
试一试embed()
> embed(x, block.size)[, block.size:1]
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 2 3 4
[3,] 3 4 5
[4,] 4 5 6
[5,] 5 6 7
[6,] 6 7 8
[7,] 7 8 9
[8,] 8 9 10
或者，sequence
matrix(
sequence(
rep(1 + length(x) - block.size, block.size),
from = head(seq_along(x), block.size)
),
ncol = block.size
)
这也给出了所需的输出
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 2 3 4
[3,] 3 4 5
[4,] 4 5 6
[5,] 5 6 7
[6,] 6 7 8
[7,] 7 8 9
[8,] 8 9 10