Add a new level to a factor and substitute existing one

Question

I\'m having a big trouble on dealing with levels names of a data frame.

I have a big data frame in which one of the colums is a factor with a LOT of levels.

Answer 1

Call make.names with unique = TRUE on your column.

df$col_foo <- factor(make.names(df$col_foo, unique = TRUE))

Answer 2

If you want all the entries to be unique then a factor does not gain you much over just using a character variable.

Probably the simplest way to do what you want is to coerce to a character vector, use the duplicated function to find the duplicates and paste something onto the end of them, then if you want use factor to recoerce it back to a factor. Possibly something like:

df$col_foo <- factor( ifelse( duplicated(df$col_fo), 
                    paste(df$col_foo, '_x', sep=''), as.character(df$col_foo)))

Answer 3

You can edit the levels of the factor variable:

levels(df$col_foo) <- c(levels(df$col_foo),"bar2_X","bar3_X")

and then change the repeated levels to one of the new levels you added.