4. Creating Graphs with ggplot | R Graph Essentials

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Table Of Contents

R Graph Essentials

4.5 (4)

R Graph Essentials

4.5 (4)

Overview of this book

This book is targeted at R programmers who want to learn the graphing capabilities of R. This book will presume that you have working knowledge of R.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Base Graphics in R – One Step at a Time

1. Base Graphics in R – One Step at a Time

Learning basic graphics techniques

Creating and joining points

Creating scatterplots and line plots

Colors in R

Passing parameter values to titles and labels

Including a regression line

Graphing mathematical functions

R provides many options

Creating graphs with several curves

Customizing your axes

Creating axis labels

Creating multiple graphs on the same page

Saving your graphs

Including mathematical expressions on your plots

Summary

2. Advanced Functions in Base Graphics

2. Advanced Functions in Base Graphics

Reading datasets into R

Including a regression line and residuals

A medical dataset to create graphs

Creating complex multiple axes

Including a grid on your graph

Shading and coloring your graph

Creating bar charts

R's color palettes

Using smoothers on your graph

Creating scatterplot matrices

Summary

3. Mastering the qplot Function

3. Mastering the qplot Function

About qplot

The qplot syntax

Producing scatterplots using qplot

Subsetting your data before graphing

Mapping aesthetics to categorical variables

Controlling colors on your graph

Setting up graphs as objects

Creating facet plots

Creating line graphs using qplot

Creating multiple curves simultaneously

Including smoothed curves

Creating histograms with qplot

Creating facet plots for histograms

Creating kernel density plots

Creating bar charts

Creating boxplots

Creating graphs with dates

Summary

4. Creating Graphs with ggplot

4. Creating Graphs with ggplot

Getting started with ggplot

Mapping color, shape, and size to a variable

Creating attractive color schemes

Creating curves for each factor level

Creating histograms

Creating bar charts

Creating boxplots

Labeling points with text

Including regression lines

Summary

Index

Index

Creating bar charts

Bar charts are useful for comparing the numbers of elements within subgroups of a population. However, they can be used for other purposes, such as comparing the means of a continuous variable across the levels of a categorical variable. You can create bar charts in ggplot using geom_bar(). As an exercise, create a bar chart of numbers of patients by ethnicity by turning the variable ETH into a factor by using factor(). The syntax is as follows:

 W <- ggplot(T, aes(factor(ETH))) +  geom_bar() 
 W

The height of each bar gives the number of patients within each ethnicity. As an exercise, you can create a horizontal bar chart by adding the layer coord_flip(). The coord_flip() layer also works for other types of graph, including scatterplots and bar charts.

Now we insert our choice of color and border color using fill and color. Let's have an ivory color for the bars, along with dark green borders. The syntax is as follows:

W + geom_bar(fill="ivory", color="darkgreen")...

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