ABSTRACT
In order to successfully merge two or more data frames, this chapter shows that they are in the same format. It looks at some of the important formatting issues and how to reformat students' data frames so that they can be easily merged. Before doing anything to their data, it is a good idea to ‘look at it’ to see what needs to be done. Taking a little time to become acquainted with their data will help students avoid many error messages and much frustration. It is often a good idea if their data sets are kept in data frame type objects if that is the format students will use for analysis. Long-formatted time-series cross-sectional data is a data frame where rows identify observations of a particular subject at particular points in time and there are multiple observations per subject.
