Man does not live by bread alone, so it would behave you to learn additional tools in addition to R, so as to advance your analytic skills:
- SQL: SQL is a valuable tool to know, regardless of which language/package/environment you choose to work in. Virtually every analytics tool will have a SQL interface, and knowledge of how to optimize SQL queries will definitely speed up your productivity, especially if you are doing a lot of data extraction directly from a SQL database. Today's common thought is to do as much pre-processing as possible within the database, so if you will be doing a lot of extracting from databases such as MySQL, PostgreSQL, Oracle, or Teradata, it will be a good thing to learn how queries are optimized ...