Introduction to R Programming
Syllabus · Features of R – Reserved words – Identifiers – Constants – Variables – Operators – Operator Precedence – Strings – Basic Data Types Chapter 1 & 2.1-2.2
R is an open-source programming language and environment designed specifically for statistical computing and graphics. It is widely used by statisticians, data scientists, and researchers. R was created by Ross Ihaka and Robert Gentleman at the University of Auckland, New Zealand. The name "R" comes from the first letter of their first names.
- Initial version released in 1995, stable beta in 2000.
- R inherits features from the S language.
- Core written in C, Fortran, and R itself.
- Freely available under GNU General Public License. Works on Linux, Windows, and Mac.
- Provides both command-line and graphical interfaces.
R has become the world's most widely used statistics programming language because of its rich set of features. Unlike many other statistical tools, R is not just a point-and-click software—it is a full programming language. This means you can write scripts, create functions, and automate complex workflows. The table below summarizes the key features, but let's understand each one in simple terms.
Before you can write R programs, you need to install the R software on your computer. The installation process is straightforward, but the steps differ slightly depending on your operating system. R is free and runs on Windows, Mac, and Linux.
sudo apt-get install r-base (Debian/Ubuntu) or yum install R (Red Hat/Fedora).There are three main ways to run R code: interactively at the command prompt, as a script file, or using a GUI.
Command Prompt (Interactive) – type R at terminal, then commands at > prompt.
> first_str <- ello="" world=""> first_str
[1] "Hello World!" R Script File – save code in .R file and run with Rscript test.R.
# test.R
str <- code="" ello="" str="" world="">GUI (RStudio or RGui) – open script, select lines, Ctrl+R to run.
Single-line comment: # comment – everything after # is ignored. R does not support multi-line comments like /* ... */ or triple quotes.
# This entire line is a comment
x <- 10="" 42="" a="" after="" assign="" code="" comment="" is="" statement="" sum="" this="" to="" valid="" x="" y="" z="">Reserved words (keywords) have special meaning in R. You cannot use them as variable names.
| if | else | repeat | while | function |
|---|---|---|---|---|
| for | in | next | break | TRUE |
| FALSE | NULL | Inf | NaN | NA |
| NA_integer_ | NA_real_ | NA_complex_ | NA_character_ | ... |
Important: R is case-sensitive. TRUE is reserved, but True is not (though strongly discouraged).
An identifier is the name you give to a variable, function, or object. Rules:
- Can contain letters (a-z, A-Z), digits (0-9), period (.), underscore (_).
- First character must be a letter or a period. If starting with period, second character cannot be a digit.
- Cannot use reserved words.
total, Sum, .date.of.birth, Sum_of_two, Rank2
tot@1, 2um, _prod, TRUE, .0wl
Best practice: Use periods as separators (e.g., a.variable.name) or underscores (a_variable_name).
Constants (literals) are fixed values. R has numeric, integer, complex, character, and logical constants.
3.14 numeric (default)42L integer (L suffix)3+4i complexpi, letters, LETTERS, month.name built-inA variable is a named storage location. R is dynamically typed – type is determined by the value assigned.
Assignment operators: <- (most common), =, -> (rightward), <<- (global).
variable.1 = c(1, 2, 3)
variable.2 <- -="" 1="" c="" ose="" otus=""> variable.3 # FALSE becomes 0, TRUE becomes 1Dynamic typing example: a variable can change type.
var_1 <- 10i="" 10l="" 20="" 90.86="" character="" code="" complex="" integer="" morning="" numeric="" ood="" var_1="">Use ls() to list variables, rm() to remove.
Operators are symbols that tell R to perform specific mathematical, logical, or relational operations. R provides five main types.
| Operator | Description |
|---|---|
+ | Adds two vectors |
- | Subtracts second vector from first |
* | Multiplies vectors |
/ | Divides first vector by second |
%% | Remainder (modulus) |
%/% | Integer division (quotient) |
^ | Exponentiation |
a <- 20="" 2="" 30="" 3="" 40="" 4="" b="" c="" cat="" exponentiation=", (a ^ b))</code></pre>
<div class=" remainder=", (a %% b))
cat(" section-title="" um=", (a + b))
cat("> Relational Operators| Operator | Description |
|---|---|
< | Less than |
> | Greater than |
<= | Less than or equal to |
>= | Greater than or equal to |
== | Equal to |
!= | Not equal to |
| Operator | Description |
|---|---|
! | Logical NOT |
& | Element-wise AND |
&& | AND (first element only) |
| | Element-wise OR |
|| | OR (first element only) |
In R, any number greater than 1 is considered TRUE in logical operations; zero is FALSE.
| Operator | Description |
|---|---|
<-, <<- | Leftwards assignment (normal / global) |
->, ->> | Rightwards assignment |
= | Leftwards assignment (similar, but different precedence) |
| Operator | Description |
|---|---|
: | Sequence (e.g., 3:9 creates 3 4 5 6 7 8 9) |
%in% | Membership – checks if element belongs to a vector |
%*% | Matrix multiplication |
When an expression contains multiple operators, R evaluates them in order of precedence. Higher precedence first.
| Operator | Description | Associativity |
|---|---|---|
^ | Exponent | Right to Left |
-x, +x | Unary minus/plus | Left to Right |
%% %/% | Modulus, integer division | Left to Right |
* / | Multiplication, division | Left to Right |
+ - | Addition, subtraction | Left to Right |
< > <= >= == != | Relational | Left to Right |
! | Logical NOT | Left to Right |
& && | Logical AND | Left to Right |
| || | Logical OR | Left to Right |
<- <<- | Leftward assignment | Right to Left |
= | Assignment | Right to Left |
# Examples
2 ^ 3 * 4 # (2^3)*4 = 32
2 + 3 * 4 # 2 + 12 = 14
(2 + 3) * 4 # 20
10 - 5 - 2 # (10-5)-2 = 3
2 ^ 3 ^ 2 # 2^(3^2) = 512Strings are sequences of characters. You can use single or double quotes.
S <- code="" e="" ello="" he="" morning="" ood="" oodbye="" quote_str1="" quote_str2="" r="" replied="" said="" world="">readline(prompt="Enter: ") reads user input from console.
R's fundamental data types include numeric, integer, complex, logical, and character.
10.5 decimal (default)
42L whole with L suffix
3+4i real + imaginary
TRUE / FALSE boolean values
"text" strings
| Data Type | Description | Example |
|---|---|---|
| numeric | Decimal numbers (default) | x <- 10.5 |
| integer | Whole numbers (use L) | x <- 10L |
| complex | Real + imaginary part | x <- 3 + 4i |
| logical | TRUE / FALSE | x <- TRUE |
| character | Text / string | x <- "Hello" |
| Function | Purpose |
|---|---|
class(x) | Returns data type of x |
is.numeric(x) | Checks if numeric |
is.integer(x) | Checks if integer |
is.complex(x) | Checks if complex |
is.logical(x) | Checks if logical |
is.character(x) | Checks if character |
as.numeric(x) | Converts to numeric |
as.integer(x) | Converts to integer |
as.complex(x) | Converts to complex |
as.logical(x) | Converts to logical |
as.character(x) | Converts to character |
Quick Reference Card
<- assignment # comment print() / cat()
class() / typeof() ls() list variables rm() remove
start:end sequence %in% membership readline() user input
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