In this tutorial, we will learn,
For Loop Syntax and Examples For Loop over a list For Loop over a matrix
For Loop Syntax and Examples
For (i in vector) { Exp }
Here, R will loop over all the variables in vector and do the computation written inside the exp.
For Loop in R Let’s see a few examples. For Loop in R Example 1: We iterate over all the elements of a vector and print the current value.
Create fruit vector
fruit <- c(‘Apple’, ‘Orange’, ‘Passion fruit’, ‘Banana’)
Create the for statement
for ( i in fruit){ print(i) }
Output:
[1] “Apple”
[1] “Orange”
[1] “Passion fruit”
[1] “Banana”
For Loop in R Example 2: creates a non-linear function by using the polynomial of x between 1 and 4 and we store it in a list
Create an empty list
list <- c()
Create a for statement to populate the list
for (i in seq(1, 4, by=1)) { list[[i]] <- i*i } print(list)
Output:
[1] 1 4 9 16
The for loop is very valuable for machine learning tasks. After we have trained a model, we need to regularize the model to avoid over-fitting. Regularization is a very tedious task because we need to find the value that minimizes the loss function. To help us detect those values, we can make use of a for loop to iterate over a range of values and define the best candidate.
For Loop over a list
Looping over a list is just as easy and convenient as looping over a vector. Let’s see an example
Create a list with three vectors
fruit <- list(Basket = c(‘Apple’, ‘Orange’, ‘Passion fruit’, ‘Banana’), Money = c(10, 12, 15), purchase = FALSE) for (p in fruit) { print(p) }
Output:
[1] “Apple” “Orange” “Passion fruit” “Banana”
[1] 10 12 15
[1] FALSE
For Loop over a matrix
A matrix has 2-dimension, rows and columns. To iterate over a matrix, we have to define two for loop, namely one for the rows and another for the column.
Create a matrix
mat <- matrix(data = seq(10, 20, by=1), nrow = 6, ncol =2)
Create the loop with r and c to iterate over the matrix
for (r in 1:nrow(mat))
for (c in 1:ncol(mat))
print(paste(“Row”, r, “and column”,c, “have values of”, mat[r,c]))
