同时循环遍历 2 个向量并保存在新向量中

Question

我有 2 个向量：

index <- as.integer(c(3, 5, 7))
sen <- c("first", "second", "third", "fourth", "fifth", "sixth", "seventh")

我想根据新向量中的索引保存每个字符串：

 mySen <- vector(mode = "character", length = length(index))

这样

> mySen
[1] "third"
[2] "fifth"
[3] "seventh"

我尝试过嵌套循环，但它们输出的索引 i 和 j 的长度为 6

for (j in index){
  for(i in 1:length(index)){
    print(c(i,j))
  }
}

[1] 1 3
[1] 2 3
[1] 3 3
[1] 1 5
[1] 2 5
[1] 3 5
[1] 1 7
[1] 2 7
[1] 3 7

而我想要索引

1 3
2 5
3 7

最重要的是，我希望我的新向量 mySen 如前所述正确填写

> mySen
[1] "third"
[2] "fifth"
[3] "seventh"

Answer 1

你可以用index子集sen

mySen <- sen[index]
mySen
#[1] "third"   "fifth"   "seventh"