S. Richter-Walsh demonstrates what the forcats R package can do:
Synonymous factor levels
Sometimes a categorical variable may have two or more factor levels that refer to the same group. There may be subtle differences in syntax such as upper case leading letter versus lower case leading letter (GroupA vs. groupA), for example. In this situation, one can use forcats::fct_collapse() to collapse the synonymous levels into one. In our test data, let’s assume that Web and Online refer to the same sales channel and we want to combine both into a factor level called Online….
df$sales <- fct_collapse(df$sales, Online = c("Online", "Web"))
I don’t use forcats that often, but when I do, I definitely appreciate it being here. H/T R-Bloggers