forcats 0.4.0

New features

• fct_collapse() gains a group_other argument to allow you to group all
  un-named levels into "Other". (#100, @AmeliaMN)

• fct_cross() creates a new factor containing the combined levels from two
  or more input factors, similar to base::interaction (@tslumley, #136)

• fct_inseq() reorders labels in numeric order, if possible (#145, @kbodwin).

• fct_lump_min() preserves levels that appear at least min times (can also
  be used with the w weighted argument) (@robinsones, #142).

• fct_match() performs validated matching, providing a safer alternative to
  f %in% c("x", "y") which silently returns FALSE if "x" or "y"
  are not levels of f (e.g. because of a typo) (#126, @jonocarroll).

• fct_relevel() can now level factors using a function that is passed the
  current levels (#117).

• as_factor() now has a numeric method. By default, orders factors in numeric
  order, unlike the other methods which default to order of appearance.
  (#145, @kbodwin)

Minor bug fixes and improvements

• fct_count() gains a parameter to also compute the proportion
  (@zhiiiyang, #146).

• fct_lump() now does not change the label if no lumping occurs
  (@zhiiiyang, #130).

• fct_relabel() now accepts character input.

• fct_reorder() and fct_reorder2() no longer require that the summary
  function return a numeric vector of length 1; instead it can return any
  orderable vector of length 1 (#147).

• fct_reorder(), fct_reorder2() and as_factor() now use the ellipsis
  package to warn if you pass in named components to ... (#174).