The lapply() function in R is “used to apply a function to a list, data frame or a vector, returning a list of the same length“.
Syntax
lapply(X, FUN)
Parameters
- X: A vector or an object.
- FUN: Function applied to each element of X.
Example 1: Iterate over a vector using the lapply() function
movies <- c("Titanic", "BATMAN", "Venom", "Conjuring")
movies_lower <- lapply(movies, tolower)
print(str(movies_lower))
Output
List of 4
$ : chr "titanic"
$ : chr "batman"
$ : chr "venom"
$ : chr "conjuring"
NULL
First, we defined a vector and used the lapply() function to convert all the elements to the small case.
Example 2: Iterate over a list using the lapply() function
list_new <- list(
A = c(11, 19, 21, 46),
B = data.frame(x = 1:5, y = c(1, 2, 3, 7, 8))
)
lapply(list_new, sum)
Output
$A
[1] 97
$B
[1] 36
Example 3: Use lapply() function with multiple arguments
list_new <- list(
A = c(11, 19, 21, 46),
B = c(1, 2, 3, 4)
)
lapply(list_new,
quantile,
probs = c(0.25, 0.50)
)
Output
$A
25% 50%
17 20
$B
25% 50%
1.75 2.50
Example 4: Use lapply() with a custom function
You can also apply a custom function with the “lapply()” function.
vec <- 1:3
# Function to calculate the third power
fun <- function(x) {
x ^ 3
}
# Applying our own function
lapply(vec, fun)
Output
[[1]]
[1] 1
[[2]]
[1] 8
[[3]]
[1] 27
Further reading

Krunal Lathiya is a Software Engineer with over eight years of experience. He has developed a strong foundation in computer science principles and a passion for problem-solving. In addition, Krunal has excellent knowledge of Data Science and Machine Learning, and he is an expert in R Language.