GETTING STARTED WITH R: VARIABLES, VECTORS, MATRICES

Vladimir E. Bakhrushin,Professor, D. Sc.

Vladimir.Bakhrushin@gmail.com

General information

R is an object-oriented programming language and environment. Its distinguishing feature is the existence of a large number of libraries for statistical data analysis.

R is a free software with open source. Another peculiarity is that R can be used in all operating systems, particularly in Windows, Linux, Mac OS, etc.

In 1997 the CRAN (Comprehensive R Archive Network (http://cran.r-project.org) project was created. It is a repository containing R system, libraries, materials and other related to R resources.

Starting message

Working Directory

By default, the program and data are stored and looking for in the working directory. We can determine, which directory is the working, with the command:

> getwd().

To change the working directory we can with the command:> setwd(“…”)

In brackets it is necessary to specify the path to correct directory.

In RGui it can also be done by selecting in the menu "File - Change Folder".

ScriptsTo create programs scripts are used. They can be written with

any text editor or in a special window that arises when selecting in the main menu "File - New script".

To open existing scripts you must choose in the main menu: "File - Open the script."

Vectors

The basic structure of R is a vector. Its elements are one or more data values of the same type. Scalar value can be represented as a vector containing a single element. More complex structures – matrices, arrays, etc. can be created from the vectors.

Vector elements may belong to such data types: numeric, integer, character, complex, logical, raw etc.

NaN is the result of calculations caused indeterminate forms 0/0, ∞/∞, ∞ − ∞ etc.

NA is used as a symbol of uncertain at the moment value (analog of NULL for database management systems).

Creating vectors with function с()

Creating vectors with function seq()

Some functions for operating with vectors

Functions

min(x)

max(x)

prod(x)sum(x)

sort(x)

var(x)

mean(x)length(x)

Matrices

Any vector can be transformed into a matrix by specifying the way of its elements placing in this matrix.

Function m=matrix(data = y, nrow = n, ncol = m) places the elements of vector y into matrix m of nm dimension so that initially the first column is filled from top to bottom, then the second, etc.

If the vector length is lower then nm, its elements are used again, starting with the first. If the length of the vector is more than nm, then some of its elements remain unused .

It is possible to combine two vectors into the matrix using the function c().

Creating matrixes

Creating matrices

Accessing the elements of vectors and matrices

Summation of vectors and matrixes elements

Transformation of vectors and matrices elements

Transformation of vectors and matrices elements

Arrays

Vectors and matrixes are special cases of arrays having, respectively, one or two dimensions.

In general, to create an array function array(<data vector>, <dimension vector>) is used.

<Data vector> is the vector of numbers from which the array is formed.

<Dimension vector> is a vector of length one or more giving the number of dimensions and maximal indices in each dimension.

Arrays

Arrays