Example: DETECT F/U Interviews Public - Check MedStar IDs across multiple data frames

# Overview

I've been working on modifying some code Ebie wrote to check to see which MedStar IDs were present in some of the F/U interview data sets, but missing from the consent form data set. Then, check to see what, if anything, should be done about it.

This seems like it would be a good case study for Intro to R and/or for Epi-Workbench. 