Functional Programming Problem Using purr and R's data.table shift function

?s 06:50 de 31/12/2022, Michael Lachanski escreveu:
Hello,

I am trying to make a habit of "functionalizing" all of my code as
recommended by Hadley Wickham. I have found it surprisingly difficult to do
so because several intermediate features from data.table break or give
unexpected results using purrr and its data.table adaptation, tidytable.
Here is the a minimal working example of what has stumped me most recently:

===

library(data.table); library(tidytable)

minimal_failing_function <- function(A){
   DT <- data.table(A)
   DT[ , A:= shift(A, fill = NA, type = "lag", n = 1)] %>% `[`
   return(DT)}
# works
minimal_failing_function(c(1,2))
# fails
tidytable::pmap_dfr(.l = list(c(1,2)),
                     .f = minimal_failing_function)

===
These should ideally give the same output, but do not. This also fails
using purrr::pmap_dfr rather than tidytable. I am using R 4.2.2 and I am on
Mac OS Ventura 13.1.

Thank you for any help you can provide or general guidance.

==
Michael Lachanski
PhD Student in Demography and Sociology
MA Candidate in Statistics
University of Pennsylvania
mikelach at sas.upenn.edu

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and provide commented, minimal, self-contained, reproducible code.
Hello,

Use map_dfr instead of pmap_dfr.

library(data.table)
library(tidytable)

minimal_failing_function <- function(A) {
   DT <- data.table(A)
   DT[ , A:= shift(A, fill = NA, type = "lag", n = 1)] %>% `[`
   return(DT)
}

# works
tidytable::map_dfr(.x = list(c(1,2)),
                    .f = minimal_failing_function)
#> # A tidytable: 2 ? 1
#>       A
#>   <dbl>
#> 1    NA
#> 2     1

Hope this helps,

Rui Barradas

Functional Programming Problem Using purr and R's data.table shift function

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