Introduction
Graphs serve a couple of important functions in data analysis. First, when exploring data, they can help us understand our data and the relationships in it.
But data analysis isn't all about wrangling data and crunching numbers. We must also communicate our findings and convey evidence for our arguments. Graphs serve an important role in succinctly communicating complex relationships. Although graphs can be unclear, confusing, or not too informative, well-made graphs can clarify concepts and relationships that are difficult to explain verbally.
Designing good, informative, and beautiful charts is difficult, and if you want to dive into that topic, and there's a lot of good information out there. Anything by Edward Tufte (http://www.edwardtufte.com/tufte/) is an excellent place to start, and his book, The Visual Display of Quantitative Information, is considered a classic in the field of data visualization design. To create charts and graphs, there are a number of options...