# This is an R-script to familiarize you with R,
#  and show you some of the plotting commands. 
# Lines starting with `#' contain comments and explanations.
#  to get help on any command, type `?' before the command


#######################
# Some general things #
#######################

# You can use R as a calculator:
5+3

# Create a vector, using the command 'c()' (for concatenate)
x <- c(1,2,3,4)
x

# Sum all elements of x:
sum(x)

# Square all elements of x:
x^2

# Get the third element of x:
x[3]

# Add an extra element:
x <- c(x,10)
x

# Create a vector using the command 'seq()' (for sequence)
x <- seq(from=1, to=10, by=.1)
x

# Obtain the length of x:
length(x)

# Create a vector using the command 'rep()' (for repeat)
x <- rep(0,times=10)
x


####################
# load a data set: #
####################

# load the car library which contains all data sets:
# (Before you can do this, you need to install the package 'car',
#  using the menu: Packages -> Install Package(s)
#  You only need to do this once on each computer you work on.)
library(car)

# Get a description of the data set `Duncan':
?Duncan

# Load the data set:
data(Duncan)

# Look at the data:
Duncan

# Get summary of the data:
summary(Duncan)

# If there are missing values, then these are denoted by 'NA'


#####################################
# Access various parts of the data: #
#####################################

# The data are stored in a matrix. 
# We can access the entries in the data set. For example, 
# for the entry in the second row and the third column:
Duncan[2,3]

# Obtain the first column:
Duncan[,1]

# Obtain the first row:
Duncan[1,]

# We can exclude a column or row by using the minus sign:
Duncan[,-1]

# We can also access the columns by their names, using a $ sign to 
# separate the name of the data set and the name of the column:
Duncan$income

# Note that the following doesn't work:
income

# But if we first attach the data, it does work:
attach(Duncan)
income

# This can save you some typing.
# To detach the dataset, use the command `detach(Duncan)' or `detach()'