在向量的每个其他元素上粘贴一个字符串

Question

我有这样的矢量：

test <- c("a","b","c","d")
test
[1] "a" "b" "c" "d"

我想粘贴一个字符串，例如“_2”，在向量的每个其他元素上，得到这个：

"a" "b_2" "c" "d_2"

我试过这个命令：

ifelse(test %in% seq(1, length(test), 2), test, paste(test, "_2", sep=""))

但这只是给了我：

"a_2" "b_2" "c_2" "d_2"

这是错误的。有关如何正确执行此操作的任何建议？谢谢！

Answer 1

怎么样

paste0(c("a","b","c","d"), c("", "_2"))

[1] "a"   "b_2" "c"   "d_2"

Answer 2

另一种选择是，

test[c(FALSE, TRUE)] <- paste0(test[c(FALSE, TRUE)], '_2')
test
#[1] "a"   "b_2" "c"   "d_2"

Answer 3

x <- c("a","b","c","d")
x[seq(2, length(x), by=2)] <- paste0(x[seq(2, length(x), by=2)], "_2")
x

这给出了：

"a"   "b_2" "c"   "d_2"