argument drop.empty not working in sjt.xtab function from sjPlot package

Lets say I have a factor level that I need to delete for the analysis for whatever reasons. I make a subset, but the factor level still exists.

Luckily, there is an argument in sjt.xtab that specifies:

drop.empty: Logical, if TRUE and the variable’s values are labeled, values that have no observations are still printed in the table (with frequency 0). If FALSE, values / factor levels with no occurrence in the data are omitted from the output.

Source: https://cran.r-project.org/web/packages/sjPlot/sjPlot.pdf

But it isn't working. Here is a minimal working example:

color <- factor(c("blue", "yellow", "red", "red", "blue"))
object <- factor(c("table", "chair", "table", "chair", "chair"))
df <- data.frame(color, object)

sjPlot::sjt.xtab(df$color, df$object) # We decide to delete "yellow" case(s)

df <- subset(df, color == "red" | color == "blue")
sjPlot::sjt.xtab(df$color, df$object, drop.empty = FALSE) 

Does anybody knows why is it not working?

I know we could use the droplevels() function but I would like to know if I am doing something wrong with the drop.empty argument

Best,

It seems that you are confusing factor labels, which are base R, and variable labels, which are implemented in some packages such as haven.

Here is an example:

library(tidyverse)
library(sjPlot)
#> Learn more about sjPlot with 'browseVignettes("sjPlot")'.
data(efc)
x = efc %>% filter(e42dep!=4) %>% pull(e16sex)
y = efc %>% filter(e42dep!=4) %>% pull(e42dep)
sjPlot::sjt.xtab(x, y, drop.empty=TRUE) 

sjPlot::sjt.xtab(x, y, drop.empty=FALSE) 

^{Created on 2022-07-04 by the reprex package (v2.0.1)}

As you used the crosstable tag, note that you can use the crosstable package as well for this kind of work (disclaimer: I'm the creator of the package).

However, there is no drop.empty option yet so you have to use forcats::fct_drop() to get rid of them beforehand. I should definitely add this kind of option someday!

Here is some code:

color <- factor(c("blue", "yellow", "red", "red", "blue"))
object <- factor(c("table", "chair", "table", "chair", "chair"))
df <- data.frame(color, object)
library(tidyverse)
library(crosstable)
df %>% 
  mutate(color=fct_drop(color)) %>% 
  crosstable::crosstable(color, by=object) %>% 
  as_flextable()

df %>% 
  mutate(color=fct_drop(color)) %>% 
  crosstable::crosstable(color, by=object, test=TRUE) %>% 
  as_flextable(compact=TRUE)

^{Created on 2022-07-04 by the reprex package (v2.0.1)}