You can use the **source** function in R to reuse functions that you create in another R script.

This function uses the following basic syntax:

source("path/to/some/file.R")

Simply add this line to the top of your R script and you’ll be able to use any functions defined in **file.R**.

The following example shows how to use the **source** function in practice.

**Example: Using the source Function in R**

Suppose we have the following R script called **some_functions.R** that contains two simple user-defined functions:

#define function that divides values by 2 divide_by_two <- function(x) { return(x/2) } #define function that multiplies values by 3 multiply_by_three <- function(x) { return(x*3) }

Now suppose we’re currently working with some R script called **main_script.R**.

Assuming** some_functions.R** and **main_script.R** are located within the same folder, we can use source at the top of our **main_script.R** to allow us to use the functions we defined in the **some_functions.R** script:

**source("some_functions.R")
#create data frame
df <- data.frame(team=c('A', 'B', 'C', 'D', 'E', 'F'),
points=c(14, 19, 22, 15, 30, 40))
#view data frame
df
team points
1 A 14
2 B 19
3 C 22
4 D 15
5 E 30
6 F 40
#create new columns using functions from some_functions.R
df$half_points <- divide_by_two(df$points)
df$triple_points <- multiply_by_three(df$points)
#view updated data frame
df
team points half_points triple_points
1 A 14 7.0 42
2 B 19 9.5 57
3 C 22 11.0 66
4 D 15 7.5 45
5 E 30 15.0 90
6 F 40 20.0 120
**

Notice that we’re able to create two new columns in our data frame using functions that we defined in the **some_functions.R** script.

The **source** function allowed us to use the **divide_by_two** and **multiply_by_three** functions in our current script, even though these functions weren’t created in the current script.

**Note**: In this example, we only used one **source** function at the top of the file. However, we can use as many **source** functions as we’d like if we want to reuse functions defined in several different scripts.

**Additional Resources**

The following tutorials explain how to use other common functions in R:

How to Use the View() Function in R

How to Use the aggregate() Function in R

How to Use the replace() Function in R