Reading this book will enable you to learn very quickly how to create wonderful graphics using R. Since R is based on syntax, the time required to master R can be considerable. However, creating high quality and attractive graphics is made easy through the syntax and step-by-step explanations of this book. By reading this book, you will learn how to introduce attractive color schemes, create headings and legends, design your own axes and axes labels, create mathematical expressions on your graphs, and much more.
Chapter 1, Base Graphics in R – One Step at a Time, introduces the basic components of a graph (headings, symbols, lines, colors, axes, labels, legends, and so on) and outlines how to use the R syntax to create these components.
Chapter 2, Advanced Functions in Base Graphics, covers the techniques required to create professional-level graphs in R, including bar charts, histograms, boxplots, pie charts, and dotcharts. It also covers regression lines, smoothers, and error bars.
Chapter 3, Mastering the qplot Function, explains how to use qplot to create a wide range of basic but attractive graphs.
Chapter 4, Creating Graphs with ggplot, introduces you to ggplot, which is an even more powerful graphics tool than qplot. We focus on the main techniques to modify your plotting background, titles, grid lines, legends, axes, labels, and colors. It also covers the essential methods to create plots using ggplot. You will learn how to create all the graph types that were covered in Chapter 1, Base Graphics in R – One Step at a Time, and Chapter 2, Advanced Functions in Base Graphics, but this time using the many special and attractive features of ggplot.
To make the most of this book, you need to install R. Go to http://cran.r-project.org/ and click on the relevant download link for either Linux, Mac, or Windows. You will also need to install a plotting package called ggplot2. You can do so within R by entering the following syntax on the command line:
install.packages("ggplot2")
If you are a senior undergraduate or postgraduate student, professional researcher, statistician, or analyst, this is the book for you. It is preferable for you to have some prior experience in R. However, even if you are new to R, you can pick up enough from this book to create publication-quality graphs.
In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The legend() command is very powerful and provides many options to create and place legends."
Any command-line input or output is written as follows:
qplot(HEIGHT, WEIGHT_1, data = T, main = "HEIGHT vs. WEIGHT", xlab = "HEIGHT (cm)", ylab = "WEIGHT BEFORE TREATMENT (kg)" , geom = "point" , colour = factor(ETH), size = 2, alpha = I(0.7))
New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "Note the use of the assigns operator, which consists of the less than sign followed by a minus sign."
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