Precombine: A command to examine n ≥ 2 datasets before combining

In this article, I present a new command, precombine, that alerts the user to, and provides assurance concerning, some problems that can occur when multiple Stata datasets are merged and appended. It describes variables that are common to multiple datasets as well as variables that are unique to one dataset. Where value labels are attached to variables, it checks whether code sets are identical across datasets. Summary statistics for values of all variables can also be listed and left in memory along with the descriptions of each variable of each dataset.