Applying data.table::transpose to a data.table that contains numerical and string values will convert everything to strings. By comparison purrr::transpose preserves the original types by creating a list of lists. Note that it is very easy to convert a list of lists to a list of vectors (that is, get the output of data.table::transpose from the output of purrr::transpose) but very hard the other way.
# Minimal reproducible example; please be sure to set verbose=TRUE where possible!
library(data.table)
dt <- data.table(num=runif(3), char = letters[1:3])
str(data.table::transpose(dt)) # I want a data.table, so fine.
# Classes ‘data.table’ and 'data.frame': 2 obs. of 3 variables:
# $ V1: chr "0.21412930265069" "a"
# $ V2: chr "0.0449177662376314" "b"
# $ V3: chr "0.299894759198651" "c"
# - attr(*, ".internal.selfref")=<externalptr>
str(data.table::transpose(as.list(dt))) # I want a list, so it should be a list of lists.
# List of 3
# $ : chr [1:2] "0.21412930265069" "a"
# $ : chr [1:2] "0.0449177662376314" "b"
# $ : chr [1:2] "0.299894759198651" "c"
library(purrr)
str(purrr::transpose(dt)) # Exactly right!
# List of 3
# $ :List of 2
# ..$ num : num 0.214
# ..$ char: chr "a"
# $ :List of 2
# ..$ num : num 0.0449
# ..$ char: chr "b"
# $ :List of 2
# ..$ num : num 0.3
# ..$ char: chr "c"
This is a very frequent operation, which is currently very hard to do with data.table. See
https://stackoverflow.com/questions/3492379/data-frame-rows-to-a-list
https://stackoverflow.com/questions/27784076/r-data-table-to-list-of-rows-better-ways
https://stackoverflow.com/questions/41005943/turn-all-data-table-rows-into-a-list-r
https://stackoverflow.com/questions/56901903/convert-a-data-table-to-list-of-rows-that-are-data-tables-and-apply-a-function-t
(and more)
Applying
data.table::transposeto a data.table that contains numerical and string values will convert everything to strings. By comparisonpurrr::transposepreserves the original types by creating a list of lists. Note that it is very easy to convert a list of lists to a list of vectors (that is, get the output ofdata.table::transposefrom the output ofpurrr::transpose) but very hard the other way.#Minimal reproducible example; please be sure to setverbose=TRUEwhere possible!This is a very frequent operation, which is currently very hard to do with
data.table. Seehttps://stackoverflow.com/questions/3492379/data-frame-rows-to-a-list
https://stackoverflow.com/questions/27784076/r-data-table-to-list-of-rows-better-ways
https://stackoverflow.com/questions/41005943/turn-all-data-table-rows-into-a-list-r
https://stackoverflow.com/questions/56901903/convert-a-data-table-to-list-of-rows-that-are-data-tables-and-apply-a-function-t
(and more)