Loops and Control Structures in R

In this section we learn about control structures loops used in R. Control structures in R contains conditionals, loop statements like any other programming languages.

Loops are very important and forms backbone to any programming languages.Before we get into the control structures in R, just type as below in Rstudio:

?control

If else statement:

#See the code syntax below for if else statement
if(x>1){
 print("x is greater than 1")
 }else{
  print("x is less than 1")
  }

#See the code below for nested if else statement

 x=10
  x=10
 if(x>1 & x<7){
     print("x is between 1 and 7")}else if(x>8 & x< 15){
         print("x is between 8 and 15")
     }

[1] "x is between 8 and 15"

For loops:

As we know for loops are used for iterating items

 #Below code shows for  loop implementation
x = c(1,2,3,4,5)
 for(i in 1:5){
     print(x[i])
 }
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5


While Loop:

 #Below code shows while loop in R
x = 2.987
while(x <= 4.987) {
     x = x + 0.987
     print(c(x,x-2,x-1))
 }
[1] 3.974 1.974 2.974
[1] 4.961 2.961 3.961
[1] 5.948 3.948 4.948
Repeat Loop: The repeat loop is an infinite loop and is used in association with Break statement
 #Below code shows repeat loop:
a = 1
 repeat { print(a) a = a+1 if(a > 4) break }
[1] 1
[1] 2
[1] 3
[1] 4

 

Break statement:
A break statement is used in a loop to stop the iterations and flow the control outside of the loop

#Below code shows break statement:
x = 1:10
 for (i in x){
     if (i == 2){
         break
     }
     print(i)
 }
[1] 1

 

Next statement:
Next statement enables to skip the current iteration of a loop without terminating it.

#Below code shows next statement 
x = 1: 4
 for (i in x) {
     if (i == 2){
         next}
     print(i)
 }
[1] 1
[1] 3
[1] 4

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