Simple lookup to insert values in an R data frame

Question

This is a seemingly simple R question, but I don\'t see an exact answer here. I have a data frame (alldata) that looks like this:

Case     zip     market
1              


        

Answer 1

Since you don't care about the market column in alldata, you can first strip it off using and merge the columns in alldata and zipcodes based on the zip column using merge:

merge(alldata[, c("Case", "zip")], zipcodes, by="zip")

The by parameter specifies the key criteria, so if you have a compound key, you could do something like by=c("zip", "otherfield").