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TRUE/FALSE and abbreviated variants T/F have different behavior when used in j #4846

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eaurele opened this issue Dec 15, 2020 · 2 comments · May be fixed by #6196
Open

TRUE/FALSE and abbreviated variants T/F have different behavior when used in j #4846

eaurele opened this issue Dec 15, 2020 · 2 comments · May be fixed by #6196
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@eaurele
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eaurele commented Dec 15, 2020

When using a logical vector in j to select columns dynamically (StackOverflow), using the abbreviations T/F has different behavior than using TRUE/FALSE

# Minimal reproducible example

library(data.table)
#> Warning: package 'data.table' was built under R version 4.0.3

DT = data.table(x=rep(c("a","b","c"),each=3), y=c(1,3,6), v=1:9)
DT[, c(TRUE, TRUE, FALSE), verbose = TRUE]
#>    x y
#> 1: a 1
#> 2: a 3
#> 3: a 6
#> 4: b 1
#> 5: b 3
#> 6: b 6
#> 7: c 1
#> 8: c 3
#> 9: c 6
DT[, c(T, T, F), verbose = TRUE]
#> Detected that j uses these columns: <none>
#> [1]  TRUE  TRUE FALSE

# `with = FALSE` still works as expected, though should no longer be necessary
# per https://stackoverflow.com/a/33301945/6197649
DT[, c(T, T, F), with = FALSE, verbose = TRUE]
#>    x y
#> 1: a 1
#> 2: a 3
#> 3: a 6
#> 4: b 1
#> 5: b 3
#> 6: b 6
#> 7: c 1
#> 8: c 3
#> 9: c 6

# Output of sessionInfo()

sessionInfo()
#> R version 4.0.2 (2020-06-22)
#> Platform: x86_64-w64-mingw32/x64 (64-bit)
#> Running under: Windows 10 x64 (build 18363)
#> 
#> Matrix products: default
#> 
#> locale:
#> [1] LC_COLLATE=English_Europe.1252  LC_CTYPE=English_Europe.1252   
#> [3] LC_MONETARY=English_Europe.1252 LC_NUMERIC=C                   
#> [5] LC_TIME=English_Europe.1252    
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#> [1] data.table_1.13.4
#> 
#> loaded via a namespace (and not attached):
#>  [1] compiler_4.0.2  magrittr_1.5    tools_4.0.2     htmltools_0.5.0
#>  [5] yaml_2.2.1      stringi_1.4.6   rmarkdown_2.3   highr_0.8      
#>  [9] knitr_1.29      stringr_1.4.0   xfun_0.16       digest_0.6.25  
#> [13] rlang_0.4.7     evaluate_0.14

Created on 2020-12-15 by the reprex package (v0.3.0)
@eaurele eaurele changed the title TRUE/FALSE and their abbreviated variants T/F have different behavior when used in j TRUE/FALSE and abbreviated variants T/F have different behavior when used in j Dec 15, 2020
@jangorecki
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jangorecki commented Dec 16, 2020 •
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Could eventually be related: https://stat.ethz.ch/pipermail/r-devel/2020-December/080317.html as we do use all.vars

> all.vars(quote(c(T,F)))
[1] "T" "F"
> all.vars(quote(c(TRUE,FALSE)))
character(0)

making workaround for that in data.table will probably be tricky because there might be T/F fields in data.table, or user defined variables in parent scope.

@MichaelChirico
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Agree w Jan -- don't use T and F is the best recommendation IMO. Probably this could be documented somewhere, maybe FAQ?

This was referenced Jun 20, 2024
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Clarify T/F versus TRUE/FALSE usage in j argument with new FAQ entry* Rdatatable/data.table
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@jangorecki @MichaelChirico @eaurele