Using R Scripts for Assignments

Assignments 1 and 2 are submitted as R scripts (.R files). This page walks you through creating, organizing, and testing your script before you submit.

Note

Starting with Assignment 3, you’ll submit Quarto documents instead. See the Quarto guide when you get there.

Step 1: Set up your project

Before writing any code, create an R Project for this assignment. See Setting Up an R Project if you haven’t done this yet.

Step 2: Create a new R script

In RStudio, go to File > New File > R Script (or press Ctrl+Shift+N / Cmd+Shift+N)
A blank script will open in the Source pane (top-left)
Save it immediately with Ctrl+S / Cmd+S — give it a descriptive name like assignment-01.R

Step 3: Add your header

Start every script with a comment block identifying yourself and the assignment:

# Assignment 1: Getting Started with R
# Your Name
# Date

Step 4: Load packages

After the header, load the packages you’ll need. Always put library() calls at the top of your script, not scattered throughout:

# Load packages
library(tidyverse)

Step 5: Write your code in sections

Use comment headers to organize your script into the parts of the assignment. This makes your code easy to read and easy to grade:

# ---- Part 1: Scatterplot ----

ggplot(mpg, aes(x = displ, y = hwy)) +
  geom_point()

# ---- Part 2: Adding Color ----

ggplot(mpg, aes(x = displ, y = hwy, color = class)) +
  geom_point()

Section headers

Lines that start with # ---- (or # ==== or # ####) create collapsible sections in RStudio. You can also jump between them using the document outline (the button at the top-right of the Source pane).

Step 6: Add comments explaining your work

Use comments to answer questions the assignment asks and to explain your reasoning:

# The scatterplot shows a negative relationship between engine size
# and highway fuel economy. Larger engines get worse gas mileage.

You don’t need to comment every line of code — just the parts where the assignment asks you to explain something or where you made a deliberate choice.

Step 7: Save your plots (if required)

Some assignments ask you to save plots as image files. Use ggsave() right after the code that creates the plot:

# Create the plot
my_plot <- ggplot(mpg, aes(x = displ, y = hwy)) +
  geom_point() +
  labs(title = "Engine Size vs. Highway MPG")

# Display it
my_plot

# Save it
ggsave("scatterplot.png", plot = my_plot, width = 6, height = 4)

Step 8: Test your script

Before submitting, make sure your script runs from start to finish without errors:

Restart R: Go to Session > Restart R (or press Ctrl+Shift+F10 / Cmd+Shift+F10)
Run everything: Go to Code > Run Region > Run All (or press Ctrl+Alt+R / Cmd+Option+R)
Check for errors: Watch the Console for red error messages

Why restart first?

During your work session, you might have created objects or loaded packages in the Console that your script depends on without realizing it. Restarting R clears everything, so you can confirm that the script is self-contained.

Step 9: Submit

Upload your .R file (and any required image files) to Canvas by the deadline.

Common mistakes

Problem	Fix
Script runs fine for you but errors on restart	You probably ran something in the Console that isn’t in your script. Add the missing code.
`library(tidyverse)` gives an error	Run `install.packages("tidyverse")` in the Console (just once — don’t put `install.packages()` in your script).
Plot doesn’t show up	Make sure you’re printing the plot object, not just assigning it. Either type the object name on its own line or use `print()`.
`object not found` error	Make sure you run the script from the top. Objects defined later in the script don’t exist until that line runs.