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In this R tutorial, we will discuss how to write a Loop. Looping statements are used to iterate the elements present in the given data structure or a given range of numbers. We will discuss for loop in R.
How to Write a Loop in R
Syntax:
for (iterator in data/sequence)
{
statements
----------
}
Data is a data structure like a vector, represents a sequence of numbers, and an iterator is a variable used to iterate the data or sequence.
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And statements are used to execute inside for loop.
Example 1: We will create a sequence of numbers from 1 to 10 and display using for loop.
for (i in 1:10){
print(i)
}
Output:
[1] 1 [1] 2 [1] 3 [1] 4 [1] 5 [1] 6 [1] 7 [1] 8 [1] 9 [1] 10
We can also perform some operations inside an iteration.
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Example 2: Sum all the elements
sum=0
for (i in 1:10){
sum=sum+i
}
print(sum)
Output:
[1] 55
Example 3: iterate through a vector and list
#create a vector
vector1=c(1:10)
#iterator through a vector
for (i in vector1){
print(i)
}
#create a list
list1=list("php","c","cpp","java","jsp")
#iterator through a vector
for (i in vector1){
print(i)
}
#iterator through a list
for (i in list1){
print(i)
}
Output:
[1] 1 [1] 2 [1] 3 [1] 4 [1] 5 [1] 6 [1] 7 [1] 8 [1] 9 [1] 10 [1] 1 [1] 2 [1] 3 [1] 4 [1] 5 [1] 6 [1] 7 [1] 8 [1] 9 [1] 10 [1] "php" [1] "c" [1] "cpp" [1] "java" [1] "jsp"
We can also specify conditions inside for loop.
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Example:
Iterate elements from 1 to 10, and if the values are more significant than 5, print greater than 5.
#create a vector
vector1=c(1:10)
#iterator through a vector
for (i in vector1){
#condition greater than 5
if(i<=5){
print(i)}else{
print("greater than 5")
}
}
Output:
[1] 1 [1] 2 [1] 3 [1] 4 [1] 5 [1] "greater than 5" [1] "greater than 5" [1] "greater than 5" [1] "greater than 5" [1] "greater than 5"
We can control the looping statements using the break keyword through conditional statements. It will terminate the loop.
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Syntax:
for (iterator in data/sequence)
{
conditional statements
----------
break
----------
other statements
----------
}
Example:
In this example, we will iterate 10 elements, and if the element is equal to 5, we will stop the iteration using the break keyword.
#create a vector
vector1=c(1:10)
#iterator through a vector
for (i in vector1){
#break when element is equal to 5
if(i==5){
break
#display
}
print(i)
}
Output:
[1] 1 [1] 2 [1] 3 [1] 4
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next
We can also control the looping statements using the next keyword through conditional statements. It will terminate the loop at a particular condition and starts looping from the next iterating element.
Syntax:
for (iterator in data/sequence)
{
conditional statements
----------
next
----------
other statements
----------
}
Example:
In this example, we will iterate 10 elements, and if the element is equal to 5, we will stop the iteration and continue again using next.
#create a vector
vector1=c(1:10)
#iterator through a vector
for (i in vector1){
# when element is equal to 5 stop the statement and continue using next
if(i==5){
next
#display
}
print(i)
}
Output:
[1] 1 [1] 2 [1] 3 [1] 4 [1] 6 [1] 7 [1] 8 [1] 9 [1] 10
Summary
From this tutorial, we discussed for loop in R along with control statements in a loop.
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