Data Types and Basic Commands in R Software

Saturday, January 12, 2013

Before you start to read this article, please visit my previous post to know how to install R software into your machine.

R has five basic or "atomic" classes of objects:

character
numeric (real numbers)
integer
complex
logical (True/False)

The most basic object is a vector

A vector can only contain objects of the same class
BUT: The one exception is a list, which represented as a vector but can contain different objects of different classes.
Empty vector can be created with the vector() function.

R objects can have attributes

names, dimnames
dimension (e.g. matrices, arrays)
class
length
other user-defined attributes/metadata

Attributes of an object can be access using attributes() function.

Factors are used to represent categorical data. Factors can be unordered or ordered. One can think of a factor as an integer vector where each integer has a label.

Factors are treated specially by modelling functions like lm() and glm()
Using factors with labels is better than using integers because factors are self-describing.

Data frames are used to store tabular data

They are represented as a special type of list where every element of the list has to have the same length
Unlike matrices, data frames can store different classes of objects in each column
Data frames also have a special attribute called row.names
Data frames are usually created by calling read.table() or read.csv()
Can be converted to a matrix by calling data.matrix()