fix/improve recode_only() with factors

[jmbarbone]

library(mark)
x <- factor(c("a", "b", "c"))
recode_only(x, c(new = "new"))
#> [1] 1 2 3
recode_only(x, c(A = "a"))
#> Warning in `[<-.factor`(`*tmp*`, m > 0, value = "A"): invalid factor level, NA
#> generated
#> [1] NA  2  3

^{Created on 2022-01-16 by the reprex package (v2.0.1)}

[jmbarbone]

I think this should do it:

recode_only.factor <- function(x, by, vals = NULL) {
  levels(x) <- mark::recode_only(levels(x), by = by, vals = vals)
  x
}