Brief Introduction to R - People.stat.sfu.ca - Simon Fraser University

STAT 430 – TUTORIAL 1Introduction to RJoslin GohSimon Fraser UniversitySept. 12, 2007

Introduction to R• Download from http://cran.stat.sfu.ca/• An R object is any vector, matrix, list, etc.• To add an object> x ls()• To remove an object, say x> rm(x)• To remove the list> rm(list =ls())

Mathematical Calculations• Addition/Subtraction> 5+5>10-2• Multiplication/Division> 5*5>10/2

Mathematical Calculations• Power multiplication> 64^(1965)> sqrt(64)• Exponentials> exp(1)• Trigonometrics> tan(pi)> sin(pi/2)> cos(pi/4)

Mathematical Calculations• Logarithms- Natural Logarithm> log(10)- Logarithm with base n> log(10,base=n)

Importing Data• To read data from a text file, say “file1.txt”> d data

Vectors• To create a vector of numbers> x1 x2 x3

Matrix• Combine vectors of numbers> x y A B

Matrix Operations• Addition and subtraction works the same as youthink.• Multiplication- A*B element multiplication- A%*%B matrix multiplication• Transpose>t(A)• Inverse>solve(A)

Distributions• Calculating the pdf> dnorm(x,mean,sd)• Calculating the cdf> pnorm(x,mean,sd)• Determining a quantile, ie inverse cdf> qnorm(x,mean,sd)• Generate a random number> rnorm(how many, mean, sd)

Type of Distributions• Uniform - unif• Binomial - binom• Negative binomial - nbinom• Poisson - pois• Gamma - gamma• Normal - norm• Exponential - exp• Chi-squared - chisq• Student t - t• F - f

Functions• Summation – sum(something)• Mean – mean(something)• Variance – var(something)• Covariance – cov(some, thing)• Correlation – cor(some, thing)

Graphics• Histogram> hist(X,xlab="x label",ylab="y label",main="My histogram")• Boxplot>plot(X,xlab="x label",ylab="y label",main="My plot“)• Plot of data according to input order>plot(X,xlab="x label",ylab="y label",main="My plot“, type=“l”)

Graphics• Adding a line on the graph> abline(h=?) for horizontal line> abline(v=?) for vertical line