"keep" argument in fct_lump_*()

[olivermagnanimous]

I'd like to be able to override the fct_lump_*() functions with a keep argument, to avoid lumping particular levels into "Other".

For example, using fct_lump_prop(), I want to lump factors that occur <20% of the time, but I want to keep "A" no matter what.

xxx <- factor(c("A", "B", "B", "C", "C", "C", "C", "C", "C", "C"))

# Desired:
fct_lump_prop(xxx, 0.2, keep = "A")
#>  [1] A     Other Other C     C     C     C     C     C     C    
#> Levels: A C Other

Adding the second part of the condition (levels(f) %in% keep) to the lvls_other() call as below would do it, I think:

fct_lump_prop <- function(f, prop, w = NULL, other_level = "Other",
                               keep = NULL) {
  f <- check_factor(f)
  check_number_decimal(prop)
  check_string(other_level, allow_na = TRUE)

  level_w <- compute_weights(f, w)
  # Compute proportion of total, including NAs
  if (is.null(w)) {
    prop_n <- level_w / length(f)
  } else {
    prop_n <- level_w / sum(w)
  }


  if (prop < 0) {
    lvls_other(f, prop_n <= -prop | levels(f) %in% keep, other_level)
  } else {
    lvls_other(f, prop_n > prop | levels(f) %in% keep, other_level)
  }
}