如何将列表中的所有向量元素更改为值

Question

列表中的每个元素对应于一个向量。我希望将向量中的所有元素更改为指定的值。例如：

x <- c("x1","x2","x3")
y <- list(1:5,1:10,1:15)
Ans <- list()
for (i in 1:length(y)){
  Ans[[i]] <- rep(x[i],length(y[[i]]))  
}

这导致：

[[1]]
[1] "x1" "x1" "x1" "x1" "x1"

[[2]]
 [1] "x2" "x2" "x2" "x2" "x2" "x2" "x2" "x2" "x2" "x2"

[[3]]
 [1] "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3"

在R中有一个函数可以处理这个问题吗？

Answer 1

我们可以将lengths与split结合使用

unname(split(rep(x, lengths(y)), rep(seq_along(x), lengths(y))))
#[[1]]
#[1] "x1" "x1" "x1" "x1" "x1"

#[[2]]
# [1] "x2" "x2" "x2" "x2" "x2" "x2" "x2" "x2" "x2" "x2"

#[[3]]
# [1] "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3" "x3"

或使用Map

Map(rep, x, lengths(y))