Joining factor levels of two columns

Question

I have 2 columns of data with the same type of data (Strings).

I want to join the levels of the columns. ie. we have:

col1   col2
Bob    John
Tom             


        

Answer 1

You want the factors to include all the unique names from both columns.

col1 <- factor(c("Bob", "Tom", "Frank", "Jim", "Tom"))
col2 <- factor(c("John", "Bob", "Jane", "Bob", "Bob"))
mynames <- unique(c(levels(col1), levels(col2)))
fcol1 <- factor(col1, levels = mynames)
fcol2 <- factor(col2, levels = mynames)

EDIT: a little nicer if you replace the third line with this:

mynames <- union(levels(col1), levels(col2))