R Programming looping statement

 

R loops

 

There may be a situation when you need to execute a block of code several number of times. In general, statements are executed sequentially. The first statement in a function is executed first, followed by the second, and so on.

Programming languages provide various control structures that allow for more complicated execution paths.

A loop statement allows us to execute a statement or group of statements multiple times and the following is the general form of a loop statement in most of the programming languages −

 

R programming language provides the following kinds of loop to handle looping requirements.

The Repeat loop executes the same code again and again until a stop condition is met.

Syntax

The basic syntax for creating a repeat loop in R is −

repeat { 

   commands 

   if(condition) {

      break

   }

}

 

Example

v <- c("Hello","loop")

cnt <- 2

 

repeat {

   print(v)

   cnt <- cnt+1

  

   if(cnt > 5) {

      break

   }

}

 

The While loop executes the same code again and again until a stop condition is met.

Syntax

The basic syntax for creating a while loop in R is −

while (test_expression) {

   statement

}

 

Here key point of the while loop is that the loop might not ever run. When the condition is tested and the result is false, the loop body will be skipped and the first statement after the while loop will be executed.

Example

v <- c("Hello","while loop")

cnt <- 2

while (cnt < 7) {

   print(v)

   cnt = cnt + 1

}

 

A For loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times.

Syntax

The basic syntax for creating a for loop statement in R is −

for (value in vector) {

   statements

}

R’s for loops are particularly flexible in that they are not limited to integers, or even numbers in the input. We can pass character vectors, logical vectors, lists or expressions.

Example

v <- LETTERS[1:4]

for ( i in v) {

   print(i)

}