• Post category:Linux
• Post author:
• Post published:14/04/2021

R is a programming language which is mainly used for statistical work. We can use `for` loops in R in different ways. We can use R `for` loop with the vector data type and in a regular way like other programming languages too.

# Syntax

The syntax of the for loop is like below.

``````for (VAL in SEQUENCE)
{
STATEMENT
}``````
• VAL is used in each iteration to set current element value.
• SEQUENCE is the list, an array of the values those will be iterated.
• STATEMENT will be executed in each iteration. We can also call is the body of the for loop.

# For Loop

We will start with a simple for loop example. We will iterate over the given list which will start from `1` and count to the `10` .We will print each element in each iteration.

```for(i in 1:10)
{
print(i)
}```

We can see that each element is printed to the standard output.

# Vector For Loop

Vector is a very popular and useful data structure in R programming language. We will create a Vector which holds years from 2015 to 2019. Then we will iterate over this vector and print each element to the standard output.

```for (year in c(2015,2016,2017,2018,2019)){
print(paste("Year:", year))
}```

# Matrix For Loop

Matrix is another useful data type used in the R programming language. We can also call matrix as multi-level array or vector. We can iterate over given matrix by using multiple and nested for loops. We will create a matrix which is 4×4 and then print to the screen accordingly.

```mymatrix <- matrix(1:16,nrow=4,ncol=4)

for(i in 1:dim(mymatrix[1])){
for(j in 1:dim(mymatrix)[2]){
mymatrix[i,j]=i*j
}
}

print(mymatrix)```

# Nested For Loop

We have all ready used some nested for loop in previous example. We can use nested or multi level loops with for like below. We will use 3 level and start from 1 to 3 and multiple them.

```for(i in 1:3){
for(j in 1:3){
for(k in 1:3){
print(i*j*k)
}
}
}```

# Using Next Statement To Skip Iteration

During the iteration of the for loop we may need to skip for specific iterations. We can use `next`  statement to skip specified iterations or cases. In this example, we will skip odd numbers.

```for(i in 1:10){
if (!i%%2){
next
}
print(i)
}```