RStudio & Running Code

Reviewed & published by Brayan K

RStudio is the standard workspace for R — a single window that combines a script editor, a live console, and panes for your variables, plots, and help, so you can write and run R comfortably.

Part of the free R course at LearnCodingFast — hands-on lessons with worked examples and the output they print, plus practice exercises and a quick quiz.

By the end of this lesson you'll know how R and RStudio relate, the difference between the console and a script, how to run code line by line or all at once, and how the working directory affects file paths.

What You'll Learn in This Lesson

• How R (the engine) and RStudio (the IDE) work together
• The difference between the console and a saved script
• How to run code line by line with Ctrl+Enter
• How to print output with cat() and message()
• How to inspect your environment with ls() and str()
• What the working directory is and how getwd() helps

1️⃣ Scripts: Code You Keep

A script is a plain text file (ending in .R) full of R commands. Unlike typing into the console, a script is a permanent record you can re-run, edit, and share. Inside RStudio you write in the top-left editor pane and send lines to the console to run them.

Notice cat() prints values without quotes and lets you mix text and numbers, while "\n" adds a line break. message() is handy for status updates that aren't part of your results.

2️⃣ The Console: Instant Feedback

The console runs code the moment you press Enter — perfect for quick checks. Two functions are invaluable for exploring: ls() lists the objects you've created, and str() ("structure") shows the shape of any object at a glance.

# In RStudio the Console (bottom-left) runs code instantly.
# Try these interactive commands to inspect your environment.

x <- 10
y <- 25

# ls() lists the variables (objects) you've created this session:
ls()                 # -> [1] "x" "y"

# Re-running a name prints its current value:
x + y                # -> [1] 35

# str() gives a compact summary of any object's structure:
str(c(1, 2, 3))      # -> num [1:3] 1 2 3

str() told us we have a numeric vector of 3 values: num [1:3] 1 2 3. You'll reach for str() constantly once you start loading real data.

3️⃣ The Working Directory

When you read or write files, R uses the working directory as its starting point. getwd() shows it; setwd("path") changes it. Getting this right prevents the most common beginner frustration: "R can't find my file."

# A typical RStudio workflow combines a script with the console.
# Working directory: where R reads and writes files by default.

# getwd()            # prints your current working directory, e.g. "/home/you/projects"

# Comments explain WHY. Use them generously in scripts.
prices <- c(9.99, 19.99, 4.50)
n_items <- length(prices)            # how many elements?

cat("You have", n_items, "items.\n") # -> You have 3 items.
cat("Most expensive:", max(prices), "\n")

Your turn. Fill in the ___ blank and run it, comparing with the expected output.

# 🎯 YOUR TURN — replace each ___ then run it.

# 1) Make a vector of three temperatures
temps <- ___   # 👉 replace ___ with c(18, 21, 16) (or three readings of your own)

# 2) Print how many readings there are with length()
cat("Readings:", length(temps), "\n")

# 3) Print the average with mean(), rounded to 1 decimal
cat("Average:", round(mean(temps), 1), "\n")

# ✅ Expected output (for c(18, 21, 16)):
# Readings: 3
# Average: 18.3

Mini-Challenge: A Session Summary

Write this one from scratch using the outline, then run it and check it against the example output.

Common Errors (and the fix)

• "cannot open file 'data.csv': No such file" — Your working directory isn't where the file lives. Run getwd() to see where you are, then setwd() or move the file.
• Console shows a + prompt — R is waiting for you to finish an unbalanced expression. Press Esc to cancel and fix the missing bracket or quote.
• Forgetting "\n" in cat() — without it, your printed lines run together. Add "\n" at the end of each cat().
• Edits don't take effect — you changed the script but ran the old console line. Re-send the edited line with Ctrl+Enter.

Pro Tips

• 💡 Use Projects: create an RStudio Project (.Rproj) per analysis — it sets the working directory automatically so file paths just work.
• 💡 Run as you write: Ctrl/Cmd+Enter runs the current line and moves to the next — the fastest way to develop.
• 💡 Restart often: Session → Restart R clears everything and proves your script works from a clean slate.

📋 Quick Reference — Running Code

🎉 Lesson Complete!

• ✅ R is the engine; RStudio is the IDE around it
• ✅ Use the console for quick tests, a script for work you keep
• ✅ Run lines with Ctrl/Cmd+Enter
• ✅ cat() and message() print to the console
• ✅ ls(), str(), and getwd() help you explore

Practice quiz

Continue this course

• Previous: Introduction to R
• Next: Vectors — R's core data structure — create, index, and do math on vectors
• Quick reference: R cheat sheet › I/O

Frequently asked questions

What is the difference between R and RStudio?

R is the actual programming language and engine that runs your code. RStudio is an IDE (integrated development environment) — a polished application that gives you a script editor, a console, a pane showing your variables, a plots viewer, and help — all in one window. You install R first, then RStudio sits on top of it. You can use R without RStudio, but RStudio makes writing and running R far more comfortable, especially for beginners.

Should I type code in the console or in a script?

Use the console for quick, throwaway experiments — checking a value or testing one line. Use a script (a .R file) for any work you want to keep, repeat, or share, because a script is a permanent record you can re-run from top to bottom. The common workflow is to write code in the script editor and send lines to the console with Ctrl+Enter (Cmd+Enter on Mac) to run them as you go.

What is a working directory and why does it matter?

The working directory is the folder R treats as 'here' — it's where R looks when you read a file like read.csv("data.csv") and where it writes files by default. Check it with getwd() and set it with setwd("path"). If R says it can't find your file, the working directory is usually the culprit. In RStudio, using Projects (a .Rproj file) sets the working directory for you automatically, which avoids most path headaches.

How do I run an entire script at once?

In RStudio, click the Source button or press Ctrl+Shift+Enter to run the whole active script. From the console you can run a saved file with source("analysis.R"). To run just a few lines, select them and press Ctrl+Enter. Running a script executes its commands in order, exactly as if you'd typed each line into the console yourself.