Outline

• Input data

• Look at data

• Extract pieces

• Basic graphing in ggplot2

Course Data

• Many commands/features in R are a part of a specific package.

• You must install and load the package in order to use these commands/features.

• We have an R package for this class. To install/update, copy and paste the following code into your RStudio source editor and run.

library(devtools)
devtools::install_github("ochyzh/classdata")

• To load the package (at the beginning of each R session if you plan to use it):

library(classdata)

Getting Help Within R

If you want to learn about a specific command:

?command
help("command")
help.search("command")
??command

R Reference Card

• http://cran.r-project.org/doc/contrib/Short-refcard.pdf

• Save/print it to reference as you work.

Your Turn (5 min)

• Install the package classdata on your computer

• Load the package into your current R session:

library(classdata)

• Look at the R help for the dataset terr_attacks

• What happens if you just type in the name of the dataset?

Exploring Objects

For any R object x, we can use any of the following:

• x

• head(x)

• summary(x)

• str(x)

• dim(x)

Try these commands on the terr_attacks data.

str is for structure

data(terr_attacks)
str(terr_attacks)

## 'data.frame':    16120 obs. of  10 variables:
##  $ country    : chr  "Afghanistan" "Albania" "Algeria" "Angola" ...
##  $ ccode      : num  700 339 615 540 160 371 900 305 373 692 ...
##  $ cabb       : chr  "AFG" "ALB" "DZA" "AGO" ...
##  $ year       : int  2001 2001 2001 2001 2001 2001 2001 2001 2001 2001 ...
##  $ type       : chr  "Armed Assault" "Armed Assault" "Armed Assault" "Armed Assault" ...
##  $ num_attacks: num  2 0 80 22 0 0 0 0 2 0 ...
##  $ GDPpc      : num  NA 2454 3617 2214 7776 ...
##  $ population : num  20531160 3060173 31590320 15562791 37471535 ...
##  $ tradeofgdp : num  NA 57.4 58.7 150.3 21.9 ...
##  $ polity2    : int  NA 5 -3 -3 8 5 10 10 -7 -8 ...

Extract Parts of an Object

• x$variable

• x[,"variable"]

• x[rows, columns]

• x$variable[rows]

rows and columns are vectors or indices.

Try these commands on the terr_attacks data.

Your Turn

• Look at the first 10 rows of the terr_attacks data

• Why are some values coded as NA? Look at the help for NA.