## Paul Johnson ## 2013-07-24 1. Review data importation and importance of data INTEGRITY. Suggest directory structure such as project data R writeup Keep data in data as provided by client. Learn to use relative directory name to access that from the R folder. "../data/data.csv". See First-R-03 for more on that. Prime Directives for Data #1. Data Integrity is Paramount Clients provide data that we DO NOT directly edit. All work should begin with pristine, unedited data file, or some file you previously created that is reproducible EXACTLY from the original, pristine file. #2. Never make point-and-click changes in anything. They are not reproducible. 2. Practice on example files. Make a project folder, make folder data in there, put this file in there simple-01.xlsx Make a directory R, in there create a file that accesses that data. 3. Discuss merging as a "real life" data problem with some examples. 4. Definitions. merge may mean "side-to-side" connection of data on same cases merge may mean "top-to-bottom" stacking of observations on different cases merge may mean "one-to-many" matching of "relational" data. 5. Step through examples of merging data data-merge-1.R data-merge-2.R 6. Homework: Merge exercise with data to be provided by C. Dowsett