get_comparisons() creates comparisons for unused groups

[benediktclaus]

get_comparisons() is a really handy function, although it creates comparisons for all factor levels and not just the ones used in the data (see below). Is this behaviour intentional or can this be fixed?

library(tibble)
library(rstatix)
#> 
#> Attache Paket: 'rstatix'
#> The following object is masked from 'package:stats':
#> 
#>     filter

factor_data <- tibble(
  groups = factor(c("a", "b"), levels = c("a", "b", "c")) 
)

factor_data
#> # A tibble: 2 x 1
#>   groups
#>   <fct> 
#> 1 a     
#> 2 b

get_comparisons(factor_data, groups)
#> $V1
#> [1] "a" "b"
#> 
#> $V2
#> [1] "a" "c"
#> 
#> $V3
#> [1] "b" "c"

^{Created on 2020-09-10 by the reprex package (v0.3.0)}

[kassambara]

Thank you for reporting this. We need to use the function droplevels() to automatically handle this issue inside the get_comparisons() function.

In the meantime, you can try the following R code:

library(tibble)
library(rstatix)
factor_data <- tibble(
  groups = factor(c("a", "b"), levels = c("a", "b", "c")) 
)
# droplevels() will drop unused  levels
get_comparisons(droplevels(factor_data), groups)

[kassambara]

fixed now, thanks