How to Iterate Over a Vector with Index in R - Step by Step Examples

How to Iterate Over a Vector with Index in R ?

To iterate over a vector with index in R, you can use a for loop along with the seq_along function or the seq_len function.

In this example,

We create a numeric vector named num_vec with several numeric values.
We use the for loop to iterate over the indices of the vector. We achieve this by using the seq_along function, which generates a sequence from 1 to the length of the vector.
Inside the loop, we print both the current index and the corresponding value from the vector using the print function. This helps us see the index-value pairs as the loop iterates through the vector.
Each iteration of the loop assigns the current index to the variable i, and the corresponding value from num_vec is accessed using num_vec[i].

num_vec <- c(10, 20, 30, 40, 50)
for (i in seq_along(num_vec)) {
    cat("Index:", i, "Value:", num_vec[i], "\n")
}

Index: 1 Value: 10
Index: 2 Value: 20
Index: 3 Value: 30
Index: 4 Value: 40
Index: 5 Value: 50

In this example,

We create a character vector named char_vec with several string values.
We use the for loop to iterate over the indices of the vector. The seq_len function is used here to generate a sequence from 1 to the length of the vector, similar to seq_along.
Inside the loop, we print both the current index and the corresponding value from the vector using the print function. This helps us observe the index-value pairs for the character vector.
Each iteration of the loop assigns the current index to the variable i, and the corresponding value from char_vec is accessed using char_vec[i].

char_vec <- c("apple", "banana", "cherry", "date")
for (i in seq_len(length(char_vec))) {
    cat("Index:", i, "Value:", char_vec[i], "\n")
}

Index: 1 Value: apple
Index: 2 Value: banana
Index: 3 Value: cherry
Index: 4 Value: date

In this tutorial, we learned How to Iterate Over a Vector with Index in R language with well detailed examples.