How to use ~ function notation using apply-family functions in R?

Question

Is there a way to use the "~." function notation with apply/lapply functions in R?

As a very simple example, I'd like to do the second of the two applies, to add "_se" to each of a list of strings:

cols <- c("x1", "x2")
sapply(cols, function(x) paste0(x, "_se")) # works, is long

sapply(cols, ~paste0(., "_se")) # doesn't work, I want to save the typing

Is there a way to do something resembling the second solution? Any other substitutes people like?

Answer 1

We don't need a loop here as paste , paste0 etc. are all vectorized

paste0(cols, "_se")
#[1] "x1_se" "x2_se"

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If we use ~ , make sure to use it with map as this works with tidyverse functions

library(purrr)
map_chr(cols, ~ paste0(.x, "_se"))
#[1] "x1_se" "x2_se"

Or another option is as_mapper

sapply(cols,  as_mapper(~ paste0(.x, "_se")))
#     x1      x2 
#"x1_se" "x2_se"