fct_lump() shouldn't relabel if no lumping occurs

[ahhaque]

If in a vector, only one value appears less than the 'prop' times, fct_lump creates a new level called 'other'. Ideally, it should keep the original level name as only one level was affected.

Example:
nRows <- 500
vec <- as.factor(c(rep("X",0.32nRows),rep("Y",0.08nRows), rep("Z",0.4nRows), rep('W', 0.2nRows)))
rebinned_vec <- fct_lump(vec, prop = 0.1)

prop.table(table(rebinned_vec)) gives the following output:
W X Z Other
0.20 0.32 0.40 0.08

In the above code, only the level 'Y' should be affected as it has less than 10% share. But since this is the only level affected, isn't it expected that fct_lump will leave the level 'Y' as it is rather than creating the 'other' level?

[davidbody]

library(forcats)

x <- as_factor(c("apple", "apple", "apple", "banana", "banana", "orange"))
fct_lump(x, 2)
#> [1] apple  apple  apple  banana banana Other 
#> Levels: apple banana Other

^{Created on 2019-01-19 by the reprex package (v0.2.1)}

[zhiiiyang]

Here is the reprex!

nRows <- 500
vec <- as.factor(c(rep("X",0.32*nRows),
                   rep("Y",0.08*nRows), 
                   rep("Z",0.4*nRows), 
                   rep('W', 0.2*nRows)))
rebinned_vec <- forcats::fct_lump(vec, prop = 0.1)

prop.table(table(rebinned_vec)) 
#> rebinned_vec
#>     W     X     Z Other 
#>  0.20  0.32  0.40  0.08
#> rebinned_vec
#>     W     X     Z Other 
#>  0.20  0.32  0.40  0.08

^{Created on 2019-01-19 by the reprex package (v0.2.1)}

[hadley]

Thanks for the reprexes! Do either of you want to take a stab at fixing this issue?

[zhiiiyang]

Thanks for the reprexes! Do either of you want to take a stab at fixing this issue?

Working on it now.