Replicate some rows in R, keeping some values constant and changing others

I have a dataset composed of political parties and their corresponding ideology. Some of these parties have changed their name, but the database does not have these renamed parties. What I want to do is duplicate rows corresponding to political parties which were renamed, keeping their ideological values constant but changing their names accordingly.

For example. Suppose I generate the following data.frame:

df <- data.frame(party = c("AB", "PQ", "HL", "AS"), ideology = c("left", "center-right", "right", "right"))

Now suppose that the party AB changed its name to RB. I want to create a new row with a party called RB and its ideology value corresponding to AB's ideology value.

How do I do this in an efficient way? In the real dataset, I have several parties that were renamed.

Solution

You can create a data.frame holding the old and the new name, extract the present information using match, overwrite the party name and use rbind to join the new data to the present.

x <- data.frame(old="AB", new="RB")

y <- df[match(x$old, df$party),]
y$party <- x$new
rbind(df, y)

#  party     ideology
#1    AB         left
#2    PQ center-right
#3    HL        right
#4    AS        right
#5    RB         left