## What is the purpose of the `apply()`

family of functions in R?

a) To apply a function to the margins of an array or a list

b) To create graphical plots in R

c) To manage memory allocation for large datasets

d) To parallelize operations across multiple cores

### Answer:

a) To apply a function to the margins of an array or a list

### Explanation:

The `apply()`

family of functions in R, which includes `apply()`

, `lapply()`

, `sapply()`

, and others, is used to apply a function to the margins of an array or a list. These functions are more efficient alternatives to looping and are particularly useful for performing operations on rows, columns, or elements of a matrix, list, or data frame.

```
# Example of using apply() on a matrix
matrix_data <- matrix(1:9, nrow = 3, byrow = TRUE)
# Applying the sum function to each row
row_sums <- apply(matrix_data, 1, sum)
print(row_sums) # Outputs: 6 15 24
```

In this example, the `apply()`

function is used to calculate the sum of each row in a matrix. The first argument is the matrix, the second argument `1`

indicates that the function should be applied to rows (use `2`

for columns), and the third argument is the function to apply. The `apply()`

family of functions is a powerful tool in R for performing repetitive operations across elements of complex data structures.