R中是否有一种简单的方法可以访问向量中负面元素的位置？

Question

say I have the following vector:

v = c(1:8)

and I would like to access the elements 7,8,1,2,3 in that order. That is, something like

v[-2:3]

would be great. Is there a simple way to access these negative positions, ie, elements from n before last to m ?

Answer 1

You could use the modulus operator (ie, the remainder):

v[-2:3 %% (length(v)+1)]

Output:

[1] 7 8 1 2 3

Answer 2

Using tail and head (different then the duplicate one):

c(tail(v,2),head(v,3))

OR we can use union to combine the answer:

union(tail(v,2),head(v,3))

Output:

[1] 7 8 1 2 3

Answer 3

以下是使用负元素位置的两个其他选项： c(v[-6:-1], v[1:3])或c(v[-c(1:6)], v[1:3])