Using R part 7: more graph examples

Part 7 of a 7 part series on using R. This series is meant to help people who would normally use Excel to analyze data and make graphs get started with R.
Part 7 shows more examples of different types of graphs. In particular, there is an example of how to reshape your data in order to make a bar graph with error bars. There is also an example of overlaying two plots on top of one another to make a more complex graph.