R Code Tutorial

Instructions

Learn how to use each of the follow R Commands by copying the Example Code and pasting it into your R Console.

data( )

Console Help Command: ?data

data()

This command lists the available datasets in R. Information about each dataset can then be viewed using the ?nameofthedataset command.

Example Code

#Run these codes in your Console to see what they do.
data()
?cars #Brings up the help file for the cars dataset.
?CO2 #Brings up the help file for the CO2 dataset.

head( )

Console Help Command: ?head

head(object)

There is a similar function called tail(object)

object is typically the name of a data.frame object in R, i.e., a dataset.

Example Code

head(cars) #Shows the first 6 rows by default.
head(cars,11) #Shows the first 11 rows.
tail(CO2) #Shows the last 6 rows by default.
tail(CO2, 10) #Shows the last 10 rows.

View( )

Console Help Command: ?View

View(object)

object is typically the name of a data.frame object in R, i.e., a dataset.

Example Code

View(cars) 
View(CO2)

$

DataSetName$ColumnName

The $ operator allows you to access the individual columns of a dataset.

Example Code

View(cars)
cars$speed
cars$dist

mean( )

Console Help Command: ?mean

mean(x)

x is a quantitative variable of data.

Example Code

mean(cars$speed)
mean(cars$dist)

Other Stats Functions	Example Code
median( )	`median(cars$dist)`
min( )	`min(cars$dist)`
max( )	`max(cars$dist)`
sd( )	`sd(cars$dist)`
summary( )	`summary(cars$dist)`
range( )	`range(cars$dist)`
quantile( )	`quantile(cars$dist, .25)`
var( )	`var(cars$dist)`
cor( )	`cor(cars$dist, cars$speed)`

table( )

Console Help Command: ?table

table(x)

This function tabulates (or counts) how many observations come from each category of a qualitative variable in a dataset.
x is a qualitative variable from a dataset.

Example Code

table(CO2$Type)
table(chickwts$feed)
table(CO2$Type, CO2$Plant) #crosstabs table

hist( )

Console Help Command: ?hist

hist(x)

x is a quantitative variable of data.

Example Code

hist(cars$dist)
hist(cars$dist, breaks=10)
hist(cars$dist, main="1920's Vehicles", xlab="Stopping Distance")

Other Stats Plots	Example Code
boxplot( )	`boxplot(cars$dist)`
stripchart( )	`stripchart(cars$dist)`
qqnorm( )	`qqnorm(cars$dist); qqline(cars$dist)`
barplot( )	`barplot(table(chickwts$feed))`

plot( )

Console Help Command: ?plot

plot(y ~ x, data=NameOfDataset)

y is the quantitative variable for the y-axis.
x is the quantitative variable for the x-axis.
NameOfDataset is the name of the dataset that contains y and x as columns.

Example Code

plot(dist ~ speed, data=cars)
plot(dist ~ speed, data=cars, pch=16)
plot(dist ~ speed, data=cars, pch=16, col="skyblue")
plot(dist ~ speed, data=cars, pch=8, col="firebrick")
plot(dist ~ speed, data=cars, pch=8, col="firebrick")

pch Options

col Options

#Run this command in your Console 
colors() #available colors in R

with( )

Console Help Command: ?with

with(datasetName, commands)

This function allows you to not have to use $ to access the columns of a dataset. It is useful sometimes, but not always.
datasetName is the name of a dataset like cars or CO2.
commands are any R Commands that need to be performed using the variables within the specified dataset.

Example Code

with(cars, mean(dist)) #same thing as: mean(cars$dist)
with(cars, cor(dist, speed)) #same as: cor(cars$dist, cars$speed)

subset( )

Console Help Command: ?subset

subset(NameOfDataset, condition)

NameOfDataset is the name of a dataset, like cars or CO2.
condition is some logical expression that uses any of the following logical connectors.

Logical Expression	Syntax
Equals	`==`
Not Equal	`!=`
Less Than	`<`
Less Then or Equal to	`<=`
Greater Than	`>`
Greater Than or Equal to	`>=`
AND	`&`
OR	`\|`
IN	`%in%`
NOT	`!`

Example Code

subset(CO2, Type=="Quebec")
subset(CO2, Type!="Quebec")
subset(CO2, conc < 175)
subset(CO2, conc <= 175)
subset(CO2, conc > 675)
subset(CO2, conc >= 675)
subset(CO2, Type=="Quebec" & conc <= 175)
subset(CO2, Plant=="Qn1" | Plant=="Mc2")
subset(CO2, Plant %in% c("Qn1","Qc3","Mn2","Mc3"))
subset(CO2, Type !="Quebec")

<-

Console Help Command: none

NameYouCreate <- some R commands

<- (Less than symbol < with a hyphen -) is called the assignment operator and lets you store the results of the some R commands into an object called NameYouCreate.
NameYouCreate is any name that begins with a letter, but can use numbers, periods, and underscores thereafter. The name should not contain spaces.

Example Code

aveSpeed <- mean(cars$speed)
aveSpeed

fastCars <- subset(cars, speed > 20)
View(cars)
View(fastCars)

fastCars$NewColumnFTperSEC <- fastCars$speed * 5280 / 3600
View(fastCars)

c( )

Console Help Command: ?c

c( )

The c( ) function combines values into a vector or list.

Example Code

c(1,3,5)
c(1:5)
c("dog","cat","bird")

animals <- c("dog","cat","bird")
animals

counts <- c(5, 2, 18)
counts

[ ]

Console Help Command: none

objectName[ elementNumber ]

objectName[ Rows, Columns]

If objectName is an object that contains a list of numbers then [ elementNumber ] will pull out the specified elements.
If objectName is an object with rows and columns (like a dataset) then the specified [ Rows , Columns] can be accessed.

Example Code

counts <- c(5, 2, 18)
counts
counts[3]   #third element
counts[2:3]  #second through third elements
counts[c(1,3)] #first and third elements

View(cars)
cars[2:3, ] #second and third rows, all columns
cars[ ,2]   #all rows, second column
cars[2,2]   #second row, second column (single item)
cars[2:3,2] #second and third rows, second column