R: for loops

“for” loop provides a compact way to iterate over a range of values.

Syntax

for(variable in sequence){

         Do some thing

}

ForEx.R

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

$ Rscript ForEx.R 
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
[1] 8
[1] 9
[1] 10

Traversing vector

You can iterate through a vector in many ways. Following example shows different ways to iterate through a vector.

TraverseVector.R

vector1 <- c(5, 6, 7, 8)

print("Way1 to traverse vector")
for(i in 1:4){
 print (vector1[i])
}

print("Way2 to traverse vector")
for(i in seq_along(vector1)){
 print(vector1[i])
}

print("Way3 to traverse vector")
for(i in vector1){
 print(i)
}

$ Rscript TraverseVector.R 
[1] "Way1 to traverse vector"
[1] 5
[1] 6
[1] 7
[1] 8
[1] "Way2 to traverse vector"
[1] 5
[1] 6
[1] 7
[1] 8
[1] "Way3 to traverse vector"
[1] 5
[1] 6
[1] 7
[1] 8

Traverse a matrix using for loop

> matrix1 <- matrix(1:9, nrow=3, ncol=3)
> matrix1
     [,1] [,2] [,3]
[1,]    1    4    7
[2,]    2    5    8
[3,]    3    6    9

PrintMatrix.R

matrix1 <- matrix(1:9, nrow=3, ncol=3)

print("printing matrix using for loop")

for(i in seq_len(nrow(matrix1))){
 for(j in seq_len(ncol(matrix1))){
  print (matrix1[i,j])
 }
  
}

$ Rscript PrintMatrix.R 
[1] "printing matrix using for loop"
[1] 1
[1] 4
[1] 7
[1] 2
[1] 5
[1] 8
[1] 3
[1] 6
[1] 9

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