Data visualization : a practical introduction This book provides students and researchers a hands on introduction to the principles and practice of data visualization. It explains what makes some graphs succeed while others fail how to make high quality figures from data using powerful and reproducible methods and how to think about data visualization in an honest and effective way. Data Visualization builds the reader’s expertise in ggplot2 a versatile visualization library for the R programming language. Through a series of worked examples this accessible primer then demonstrates how to create plots piece by piece beginning with summaries of single variables and moving on to more complex graphics. Topics include plotting continuous and categorical variables; layering information on graphics; producing effective “small multiple” plots; grouping summarizing and transforming data for plotting; creating maps; working with the output of statistical models; and refining plots to make them more comprehensible.