R Academy · Lesson

Using source() to Load Scripts

Execute external R scripts and share code across files with source().

Why Use source()?

As your R projects grow, keeping all code in one file becomes unmanageable. The source() function lets you load and execute an external R script file, splitting your work into logical, reusable modules.

This is the foundation of organized R development.

# Imagine helpers.R contains:
# add <- function(a, b) a + b
# multiply <- function(a, b) a * b

# Load it into your main script:
source('helpers.R')

# Now use the functions defined there:
result <- add(3, 5)
cat('Result:', result)

Basic source() Syntax

The simplest form of source() takes a file path as its only argument. The file is read and every expression in it is evaluated in the current environment, just as if you had typed the code directly.

# source() with a relative path (file in working directory)
source('my_functions.R')

# source() with an absolute path
source('/Users/alice/projects/utils.R')

# After sourcing, all objects and functions defined
# in the file are available in your current session
cat('Script loaded successfully')

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