Basic Syntax in R Programming

R has a simple and readable syntax that makes it easy to start programming. Understanding the basic structure of R code helps you write clean and correct programs. R executes commands line by line and provides immediate output in the console.

• R is case-sensitive (x and X are different).
• Each statement is executed separately.
• Comments are written using #.

Writing and Running Code

R code can be written in:

• R Console
• RStudio Script
• Jupyter Notebook

Example:

print("Hello, World!")

[1] "Hello, World!"

Syntax of an R Program

An R program mainly consists of:

• Variables
• Comments
• Keywords

These components form the basic structure of any R script.

1. Variables in R

Variables are used to store values so they can be reused later in the program. In R, assignment can be done in three ways:

1. = (Simple Assignment)
2. <- (Leftward Assignment)
3. -> (Rightward Assignment)

Example:

var1 = "Simple Assignment"
var2 <- "Leftward Assignment!"
"Rightward Assignment" -> var3

print(var1)
print(var2)
print(var3)

[1] "Simple Assignment"
[1] "Leftward Assignment!"
[1] "Rightward Assignment"

The rightward assignment is less common and can be confusing for some programmers, so it is generally recommended to use the <- or = operator for assigning values in R.

2. Comments in R

Comments are used to explain code and improve readability. They are ignored by the R interpreter during execution.

Example:

# This is a single line comment
print("This is fun!")

if(FALSE)
{
  "This is multi-line comment which should be put inside either a single or a double quote"
}

[1] "This is fun!"

From the above output, we can see that both comments were ignored by the interpreter.

3. Keywords in R

Keywords are reserved words in R that have special meaning. They cannot be used as variable names or function names.

• if, else, repeat, while, function, for, in, next and break are used for control-flow statements and declaring user-defined functions.
• The ones left are used as constants like TRUE/FALSE are used as boolean constants.
• NaN defines Not a Number value and NULL are used to define an Undefined value.
• Inf is used for Infinity values.

4. Semicolons and Multiple Statements

You can write multiple statements in one line using a semicolon ;

x <- 5; y <- 6; print(x + y)

[1] 11

However, writing each statement on a new line improves readability.

5. Braces and Code Blocks

Curly braces {} are used to group multiple statements together, especially in control structures and functions.

if (TRUE) {
  print("This is a block of code")
  print("Multiple lines inside braces")
}

[1] "This is a block of code"
[1] "Multiple lines inside braces"

6. Object Naming Rules

• Names can contain letters, numbers, . and _.
• Names cannot start with a number.
• Avoid using reserved words like if, else, function.

my_value <- 100
value2 <- 50

7. Printing Output

R provides different functions to display output.

print("Using print function")
cat("Using cat function\n")

[1] "Using print function"
Using cat function

• print() displays output with index numbers.
• cat() prints output in a cleaner format.