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recode_factor does not handle !!! #3390

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dan87134 opened this issue Mar 3, 2018 · 4 comments
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recode_factor does not handle !!! #3390

dan87134 opened this issue Mar 3, 2018 · 4 comments
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@dan87134
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@dan87134 dan87134 commented Mar 3, 2018

A code snippet like this

dplyr::recode_factor(x, !!! layer_key)

produces an error that says !level_key is an invalid argument type

This is the result of a question on https://community.rstudio.com/t/using-recode-factor-with-quasi-quotation/5761/5

Here is a repro

library(magrittr)
library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
set.seed(100)
x <- sample(head(LETTERS, 3), 10, replace = TRUE) %>% factor
x
#>  [1] A A B A B B C B B A
#> Levels: A B C
level_key <- list("Be", "Cool", "Amigo") %>% set_names(c("B", "C", "A"))    # set factor re-level 
level_key2 <- list(B = "Be", C = "Cool", A = "Amigo")

dplyr::recode_factor(x, !!!level_key)
#> Error in !level_key: invalid argument type

Created on 2018-03-03 by the reprex package (v0.2.0).

The problem is the use of c(...) inside of rcode_factor. Here is my analysis of the problem.

The problem is buried inside of recode_factor. It is that only functions that are implemented to use quosures can properly interpret !!!

Here is where the problem is in recode_factor:

dplyr:::recode_factor
#> function (.x, ..., .default = NULL, .missing = NULL, .ordered = FALSE) 
#> {
#>     recoded <- recode(.x, ..., .default = .default, .missing = .missing)
# ----------------------------The . problem is with c() ----
#>     all_levels <- unique(c(..., recode_default(.x, .default, 
#>         recoded), .missing))
#>     recoded_levels <- if (is.factor(recoded)) 
#>         levels(recoded)
#>     else unique(recoded)
#>     levels <- intersect(all_levels, recoded_levels)
#>     factor(recoded, levels, ordered = .ordered)
#> }
#> <environment: namespace:dplyr>

Created on 2018-03-03 by the reprex package (v0.2.0).

The problem is in the Combine, c(), function. Although in !!! layer_key !!! looks like an operator or in !!!(layer_key) it looks like a function it is neither.

It depends on the function getting the !!! layer_key in an ... argument to do something like enquo(...) so that standard evaluation is bypassed. It is enquo(or one of it's friends) that interprets !!! to turn a list into individual dot arguments.

But c() is a primitive function so it just does standard evaluation of !!! level_key which, in effect, produces a syntax kind of error.

Here is an example of a function that tries to use !!! with c()

suppressPackageStartupMessages(library(tidyverse))
f2 <- function(...) {
    c(...)
}
level_key <- list("Be", "Cool", "Amigo") %>% set_names(c("B", "C", "A"))    # set factor re-level 

f2(!!! level_key)
#> Error in !level_key: invalid argument type

Created on 2018-03-03 by the reprex package (v0.2.0).

I don't see a workaround for this.

@batpigandme
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@batpigandme batpigandme commented Mar 3, 2018

Just adding an example of what we would expect, here:

Expect:

suppressPackageStartupMessages(library(tidyverse))
set.seed(100)
x <- sample(head(LETTERS, 3), 10, replace = TRUE) %>% 
  factor
recode_factor(x, B = "Be", C = "Cool", A = "Amigo")
#>  [1] Amigo Amigo Be    Amigo Be    Be    Cool  Be    Be    Amigo
#> Levels: Be Cool Amigo

Get:

level_key <- list(B = "Be", C = "Cool", A = "Amigo")
recode_factor(x, !!!level_key)
#> Error in !level_key: invalid argument type

Created on 2018-03-03 by the reprex package (v0.2.0).

@cderv
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@cderv cderv commented Mar 3, 2018

for helping with cross reference, this issue is related to #3388 that was asked before and redirected to community.rstudio.com

@batpigandme
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@batpigandme batpigandme commented Mar 25, 2018

@cderv yeah, I think community served its purpose well— turned out it was a bug, and thus landed back here! 😁

Related: #3218

Oddly enough, it works with dplry::recode.

suppressPackageStartupMessages(library(tidyverse))
set.seed(100)
x <- sample(head(LETTERS, 3), 10, replace = TRUE) %>% 
  factor

level_key <- list(B = "Be", C = "Cool", A = "Amigo")
dplyr::recode(x, !!! level_key)
#>  [1] Amigo Amigo Be    Amigo Be    Be    Cool  Be    Be    Amigo
#> Levels: Amigo Be Cool

Created on 2018-03-25 by the reprex package (v0.2.0).

@lock
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@lock lock bot commented Sep 22, 2018

This old issue has been automatically locked. If you believe you have found a related problem, please file a new issue (with reprex) and link to this issue. https://reprex.tidyverse.org/

@lock lock bot locked and limited conversation to collaborators Sep 22, 2018
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