如何在向量列表中分离粘贴

Question

Is there is a way to separate paste function in list of vectors?
An example : I would like from this : list(c(1),c(2,3),c(4)) which give

[[1]]
[1] 1

[[2]]
[1] 2 3

[[3]]
[1] 4

Paste all values with "%" to get :

[[1]]
[1] "1%"

[[2]]
[1] "2%" "3%"

[[3]]
[1] "4%"

Answer 1

You want the lapply() function which takes a list and does the same thing to every element. The lapply() function has two principle arguments. The first is a list (or a vector). The second is a function. You can either just specify the name of the function and then pass the function's remaining arguments after that, or you can write an anonymous function. I prefer the second method since it is more reliable as what you want to do gets more complicated.

l1 <- list(c(1),c(2,3),c(4))
# using lapply
lapply(l1, paste, "%", sep = "")
# with an anonymous function
lapply(l1, function(x) paste(x, "%", sep=""))

Both of these return your desired output.

[[1]]
[1] "1%"

[[2]]
[1] "2%" "3%"

[[3]]
[1] "4%"

Answer 2

We could unlist and apply paste once as it is vectorized and change it to list with relist

relist(paste0(unlist(l1), "%"), skeleton = l1)
#[[1]]
#[1] "1%"

#[[2]]
#[1] "2%" "3%"

#[[3]]
#[1] "4%"

data

l1 <- list(c(1),c(2,3),c(4))