复制向量的每个元素，并在偶数元素中添加"a“到奇数和"b”。

Question

这是我的原始矢量(长度可以变化)

c("e1","e2","e3","e4","e5","e6","e7","e8","e9","e10")

我想复制每个元素(保持顺序)，并将"a“属性为第一次出现，"b”属性为第二次，以获得：

c("e1a","e1b","e2a","e2b","e3a","e3b","e4a","e4b","e5a","e5b","e6a","e6b","e7","e7b","e8a","e8b","e9a","e9b","e10a","e10b")

我怎样才能在R中以一种简洁的方式做到这一点呢？

Answer 1

您可以使用rep(each = 2)获取复制，然后使用paste0添加后缀字母如下所示。

这是向量回收的一个很好的例子；paste0将使用c("a", "b")元素，直到长向量的长度自动耗尽为止。因此，您可以使用原始vec的任意长度来完成此操作。许多基础和包R功能将做一些类似的事情。

vec <- c("e1","e2","e3","e4","e5","e6","e7","e8","e9","e10")
paste0(rep(vec, each = 2), c("a", "b"))
#>  [1] "e1a"  "e1b"  "e2a"  "e2b"  "e3a"  "e3b"  "e4a"  "e4b"  "e5a"  "e5b" 
#> [11] "e6a"  "e6b"  "e7a"  "e7b"  "e8a"  "e8b"  "e9a"  "e9b"  "e10a" "e10b"

由reprex封装创建于2018-08-07 (v0.2.0)。