Combining and Restructuring Datasets

Abstract

This chapter explains how to make major changes to the structure of a dataset. You may need to combine data from two or more different sources into one dataset. This may be as simple as attaching one dataset to the bottom or side of another (known as appending or concatenating), or it may involving using a common variable to match the observations (known as merging). Alternatively, you may need to combine the values from several variables into one variable (stacking) or split one variable into several variables (unstacking). Finally, you may need to reshape a dataset so that data that was once held in separate variables in now held in separate observations, or vice versa (also known as rotating or transposing).