Basic of R

Overview

Teaching: 5 min
Exercises: 0 min

Questions

• how to do basic arithmetics

• how to initialize a variable

• how to get help

Objectives

• R built-in function

Input to R

• In R console, the symbol > stands for R prompt.
• The # is for comment insert.
• To clean the existing environment, remove all memory in previous sessions:

> rm(list=ls())

Using R as calculator

When using R as a calculator, the order of operations is the same as you would have learned back in school.

From highest to lowest precedence:

• Parentheses: (, )
• Exponents: ^ or **
• Multiply: *
• Divide: /
• Add: +
• Subtract: -
• Other math functions: sin, cos, log1(), log10(), exp

a <- (1+2)*3-4^5
b <- sin(1)+log10(20)*exp(2)

Compare in R

• ==: equality
• !=: inequality
• <& <=: less than & less than or equal to
• >& >=: more than & more than or equal to

1==1

Assign Variables

• To assign variable in R, we can use both <- and = sign

a <- 1
b = 2

Note that assignment does not print out value to R console. It save the variable in Environment section:

• To print the variable to console

a
print(a)

The output will be like this:

> a
[1] 1
> print(a)
[1] 1

But not to worry about the [1] in front. We will be learning about that in the later part

Working directory

One important step in R is to define the working directory. It is particularly useful when you are working with files in the working directory and working in Linux environment in Palmetto:

# print working directory
getwd()
# set working directory
setwd('C:/R/') # for Windows
setwd('/user/home/R') # for Macs

Seeking Help

In order to look for help files for function:

• Put ? in front of function name, for example rnorm

?rnorm
help(rnorm)
str(rnorm)

The help section will display:

Key Points

• Use RStudio to write and run R programs.

• R has the usual arithmetic operators and mathematical functions.

• Use <- to assign values to variables.

• Use ls() to list the variables in a program.

• Use rm() to delete objects in a program.

• Use sessionInfo() to get detail of the current loaded environmemt and packages