Reference

Change order of levels Keep the values of the levels the same, but change their order. These are particularly useful for models, tables, and visualisations.
fct_relevel()	Reorder factor levels by hand
fct_inorder() fct_infreq() fct_inseq()	Reorder factor levels by first appearance, frequency, or numeric order
fct_reorder() fct_reorder2() last2() first2()	Reorder factor levels by sorting along another variable
fct_shuffle()	Randomly permute factor levels
fct_rev()	Reverse order of factor levels
fct_shift()	Shift factor levels to left or right, wrapping around at end
Change value of levels Change factor levels, while preserving order (as much as possible).
fct_anon()	Anonymise factor levels
fct_collapse()	Collapse factor levels into manually defined groups
fct_lump() fct_lump_min() fct_lump_prop() fct_lump_n() fct_lump_lowfreq()	Lump together factor levels into "other"
fct_other()	Replace levels with "other"
fct_recode()	Change factor levels by hand
fct_relabel()	Automatically relabel factor levels, collapse as necessary
Add/remove levels Leave existing data as is, but add or remove levels.
fct_expand()	Add additional levels to a factor
fct_explicit_na()	Make missing values explicit
fct_drop()	Drop unused levels
fct_unify()	Unify the levels in a list of factors
Combine multiple factors
fct_c()	Concatenate factors, combining levels
fct_cross()	Combine levels from two or more factors to create a new factor
Other helpers
as_factor()	Convert input to a factor
fct_count()	Count entries in a factor
fct_match()	Test for presence of levels in a factor
fct_unique()	Unique values of a factor
lvls_reorder() lvls_revalue() lvls_expand()	Low-level functions for manipulating levels
lvls_union()	Find all levels in a list of factors
Data
gss_cat	A sample of categorical variables from the General Social survey