矢量的圆位移距离 n

问题描述

说我有

a <- c(1, 2, 3)

并且我希望 b 通过向左"方向移动距离 1 来从 a 导出

and I want b to be derived from a by shifting it in direction "left" by distance 1

b
# [1] 2 3 1

推导我的意思是你:

1. 将a"传递给一个吐出b"的函数
2. 您使用了某种索引短文来做到这一点.
例如，
3. b <- c(2, 3, 1) 不是我要寻找的解决方案

1. Pass "a" into a function that spits out "b"
2. You use some sort of indexing short had which does that.
3. b <- c(2, 3, 1), for example, is not a solution I'm looking for

有什么优雅/有效的方法可以做到这一点?

What would be elegant/efficient ways to do that?

推荐答案

你可以利用 head 和 tail 来创建这样的函数:

You can make use of head and tail to create a function like this:

shifter <- function(x, n = 1) {
  if (n == 0) x else c(tail(x, -n), head(x, n))
}

用法:

a <- 1:4

shifter(a)
# [1] 2 3 4 1

shifter(a, 2)
# [1] 3 4 1 2

(或者，library(SOfun); shifter(a) 你可以从 ).

(Or, library(SOfun); shifter(a) where you can get SOfun from here).

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