A wrapper for base::split taking as an argument the expected number of sub-elements

split_into.R

library(magrittr)
split_into <- function(x, n, sorted=TRUE)
  ## x -- a vector (atomic or list)
  ## n -- the number of elements (groups)
  ## returns a list with n elements
  ## each containing some of the elements of x
  n %>%
  seq_len %>%
  rep.int(x %>%
            length %>%
            divide_by(n) %>%
            ceiling) %>%
  `if`(sorted, sort(.), .) %>%
  extract(seq_along(x)) %>%
  split(x,.)

## Examples:
## Unlike simple `split(letters[1:7], 1:3)`
## `split_into(letters[1:7], 3, TRUE)` does not
## produce the warning "data length is not a multiple
## of split variable" and allows sorting (i.e. putting
## original nearby elements in the same subgroups):
# split_into(letters[1:7], 3, TRUE)
## $`1`
## [1] "a" "b" "c"
## 
## $`2`
## [1] "d" "e" "f"
## 
## $`3`
## [1] "g"
# 
# split_into(letters[1:7], 3, FALSE)
## $`1`
## [1] "a" "d" "g"
## 
## $`2`
## [1] "b" "e"
## 
## $`3`
## [1] "c" "f"