InfoViz with R

Haad Khan
12th March 2015

Introduction

This presentation is about visualizing data with R

  • We are going to use R package ggplot2
  • We will talk about some principles of Information Visualization.

-Adapted from Dawn Koffman Office of Population Research Princeton University

R Package ggplot2

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  • Authored by Hadley Wickham.
  • Based on The Grammar of Graphics by Leland Wilkinson, 2005

qplot()

ggplot2 provides two ways to produce plot objects:

  • qplot() #quick plot Not covered in this presentation
  • borrows some concepts from graphics of grammer but limited in capability

  • very easy to produce basic graphs

  • ggplot() grammar of graphics

  • has a steeper learning curve but extremely powerful

Grammar Defines Components of Graphics

data: in ggplot2, data must be stored as an R data frame

coordinate system: decribes 2-D space that data is projected onto

geoms: describe type of geometric objects that represent data

aesthetics: describe visual characteristics that represent data

scales: for each aesthetic, describe how visual characteristic is converted to display values

stats: describe statistical transformations that typically summarize data

facets: describe how data is split into subsets and displayed as multiple small graphs

First Dive into ggplot2

#install.packages("ggplot2")
library(ggplot2)
ggplot(diamonds, aes(x=carat, y=price)) + geom_point()

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Creating a Line Graph

ggplot(pressure, aes(x=temperature, y=pressure)) + geom_line()

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Diamond Smoothing

ggplot(diamonds,aes(x=carat, y=price))+ geom_point()+ stat_smooth()

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Diamond Smoothing Zooming

ggplot(diamonds,aes(x=carat, y=price))+ geom_point()+ stat_smooth()+xlim(0.2,1)

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Diamond Smoothing Zooming Jitter

ggplot(diamonds,aes(x=carat, y=price))+ geom_jitter()+ stat_smooth()+xlim(0.2,1)

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Diamond Smoothing Zooming Polygon

ggplot(diamonds,aes(x=carat, y=price))+ geom_polygon()+ stat_smooth()+xlim(0.2,1)

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Diamond Smoothing Zooming Label

ggplot(diamonds,aes(x=carat, y=price))+ geom_text(label = '@')+ stat_smooth()+xlim(0.2,1)

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