Basic of R

Objects - variables

use c() to create a collection of data and assign them to a variable.

metallicaNames<-c("Lars", "James", "Kirk", "Rob")

Dataframes

A dataframe is similar to a spreadsheet, an object that containing several objects. To combine different objects.

metallica<-data.frame(Name=metallicaNames, Age=metallicaAges)

To add column to a dataframe

metallica$chidAge<-c(12, 12, 4, 6)

To see the column names of a dataframe

names(metallica)

Create a list: a list of separate objects


> metallica2<-list(metallicaNames, metallicaAges)
> metallica2
[[1]]
[1] "Lars"  "James" "Kirk"  "Rob"

[[2]]
[1] 47 47 48 46

> metallica2[1]
[[1]]
[1] "Lars"  "James" "Kirk"  "Rob"

> metallica2[2]
[[1]]
[1] 47 47 48 46

Dates

To create date type objects

birth_data<-as.Date(c("1977-07-03", "1969-05-24", "1973-06-21", "1970-07-16", "1949-10-10", "1983-11-05", "1987-10-08", "1989-09-16", "1973-05-20", "1984-11-12"))

Coding variable

It is used to indicate different groups for participants, such as "Tablet" and "Phone" group. First we create collection of different numbers to indicate the different group, and then assign them to corresponding factors using factor().


> job<-c(rep(1, 5), rep(2, 5))
> job
 [1] 1 1 1 1 1 2 2 2 2 2
> job<-factor(job, levels=c(1:2), labels=c("Lecturer", "Student"))
> job
 [1] Lecturer Lecturer Lecturer Lecturer Lecturer Student  Student  Student
 [9] Student  Student
Levels: Lecturer Student

Alternative to create coding variables

job<-gl(2, 5, labels=c("Lecturer", "Student"))

Importing data

csv -> dataframe
lecturerData2 = read.csv("Lecturer Data.dat", header=TRUE)

dat or txt -> dataframe
lecturerData2<-read.delim("Lecturer Data.dat", header=TRUE)

to navigate to different directory we could use setwd("xx/xx")

Manipulating data

select a part of data

newDataf <- oldDataf[rows, frames]

lecturerPersonality <- lecturerData[, c("friends", "alcohol", "neurotic")]
lecturerOnly <- lecturerData[job=="Lecturer",]
alcoholPersonality <- lecturerData[alcohol > 10, c("friends", "alcohol", "neurotic")]

stack the dataframe (wide -> long)

select columns to be stacked on top of each other


satisfactionStacked<-stack(satisfactionData, select=c("Satisfaction_Base", "Satisfaction_6_Months", "Satisfaction_12_Months", "Satisfaction_18_Months"))