I'm trying to do something that seems very simple, but I cannot figure it out. I have a tibble like so:
> df <- tibble::tribble(
~col_a, ~col_b,
1, "A",
2, "B",
3, "C",
)
> df
# # A tibble: 3 x 2
# col_a col_b
# <dbl> <chr>
# 1 A
# 2 B
# 3 C
and I want to turn it into a list that looks like this
> str(res_list)
# List of 3
# $ :List of 2
# ..$ col_a: num 1
# ..$ col_b: chr "A"
# $ :List of 2
# ..$ col_a: num 2
# ..$ col_b: chr "B"
# $ :List of 2
# ..$ col_a: num 3
# ..$ col_b: chr "C"
I tried a number of things using base apply and dplyr::rowwise but nothing worked quite right. In the docs for purrr::pmap I thought I found the answer:
f. A function, formula, or vector (not necessarily atomic)...
If character vector, numeric vector, or list, it is converted to an extractor function. Character vectors index by name...
So I thought, great this should work: pmap(df, c("col_a", "col_b")) and that should extract those columns for each element (row) and return a list of the extracted lists. But when I run that I get:
Error in pluck(x, "col_a", "col_b", .default = NULL) :
argument "x" is missing, with no default
I semi-understand this error, but I think I'm following the usage in the docs. Maybe this is just a bug in purrr?
Anyway, commentary on the potential purrr bug is welcome, but really I'm just trying to create this list. Any help is very appreciated.
You can use group_split() (or base split() if you prefer):
library(dplyr)
library(purrr)
df %>%
group_split(row_number(), .keep = FALSE) %>%
map(as.list)
Where str() gives:
List of 3
$ :List of 2
..$ col_a: num 1
..$ col_b: chr "A"
$ :List of 2
..$ col_a: num 2
..$ col_b: chr "B"
$ :List of 2
..$ col_a: num 3
..$ col_b: chr "C"
Or:
lapply(split(df, 1:nrow(df)),
as.list)