如何将向量中的元素相乘以用作列

Question

我有一个数据框：

a <- data.frame(c(1:10))

我想添加一个像这样的列：

a$Groups <- c("Group1","Group1","Group1",
              "Group2","Group2","Group2","Group2","Group2",
              "Group3","Group3")

但我不想重复每一个元素。

谢谢你们！

Answer 1

尝试

a$Groups <- c(rep("Group1", 3),
              rep("Group2", 5),
              rep("Group3", 2))

并查看

?rep

Answer 2

改编@ alko989的答案是使用paste和rep：

> paste0("Group", rep(1:3, c(3, 5, 2)))
 [1] "Group1" "Group1" "Group1" "Group2" "Group2" "Group2" "Group2"
 [8] "Group2" "Group3" "Group3"

或者，效率更高（我认为）：

rep(paste0("Group", 1:3), c(3, 5, 2))