Statistical Methods with R

Working in RStudio

Unit A · Chapter 01 · Lecture 01b

Developed by Jeffrey M. Girard

Roadmap: Meeting R

1. R and RStudio

2. Console

3. Scripts

4. Activity

R and RStudio

Programming is a Superpower

• Programming is how we talk to and control computers

• It gives us power and flexibility

  • The same instruction runs on ten rows or ten million
  • We are not limited to what a menu anticipated

• Everything in this course is done via programming

• Programming will leave a record of what we did (i.e., code)

  • So we can reuse it, adapt it, and share it
  • And so someone else can check it

R and Other Stats Software

• You may have met SPSS, SAS, Stata, Mplus, JASP, or jamovi
  • All of them can run the analyses in this course

• R is free, on every computer you will ever use
  • No licence to buy, renew, or lose when you change institution
  • JASP and jamovi are free too, and both are built on R

• R is a real programming language, not a menu with a syntax window
  • Which is why data preparation (cleaning, reshaping, merging) is easier

• New methods arrive as packages, years before commercial tools do

The R Ecosystem

1. Your computer is the engine of a car
   • It provides raw power for computation

2. The R language is the controls
   • It lets you apply and direct that power

3. RStudio is like a fancy dashboard for the car
   • It adds information and convenience

4. An R package is like an add-on for the car
   • It adds new features and capabilities

Installing R

Windows

1. Open a web browser
2. Visit cloud.r-project.org
3. Click “Download R for Windows”
4. Click the “base” subdirectory link
5. Click “Download R-4.X.X” (e.g., 4.6.1)
6. Run the downloaded .exe file
7. Select all the default options
8. Complete the installation wizard

Mac OS

1. Open a web browser
2. Visit cloud.r-project.org
3. Click “Download R for macOS”
4. Click “R-4.X.X-arm64.pkg” (Apple silicon) or “R-4.X.X-x86_64.pkg” (older Intel Macs)
5. Run the downloaded .pkg file
6. Select all the default options
7. Complete the installation wizard

Note. You will need to repeat this process every time a new version of R is released (every 4–5 months).

Installing RStudio

Windows

1. Open a web browser
2. Visit posit.co/download/rstudio-desktop
3. Scroll down to the RStudio IDE table
4. Find the row for “Windows”
5. Click “RStudio-2026.XX.X-XXX.exe”
6. Run the downloaded .exe file
7. Select all the default options
8. Complete the installation wizard

Mac OS

1. Open a web browser
2. Visit posit.co/download/rstudio-desktop
3. Scroll down to the RStudio IDE table
4. Find the row for “macOS 13+”
5. Click “RStudio-2026.XX.X-XXX.dmg”
6. Run the downloaded .dmg file
7. Drag the RStudio icon to your Applications folder (if you want)

Note. You will need to repeat this process every time a new version of RStudio is released (every 2–4 months).

RStudio Window

Note. You can customize RStudio (e.g., the fonts, color themes, and pane layout) under “Tools > Global Options”.

Console

R will Grant your Wishes

• R is a well-meaning but overly literal genie

  • It has the power to grant almost any wish
  • But we must phrase our wishes carefully!
  • We will always get what we ask for…
  • …but not always what we wanted.

• Mastering the R language means learning…

  • How to properly phrase commands
  • How to decipher error messages
  • How to view code from R’s perspective
  • How to find and fix small mistakes

Communicating with R

• The Console is like a chat window with R
  • You send a command to R and get a response
  • Neither side of the conversation is saved

• An R Script is like an email thread with R
  • You send many commands to R all at once
  • Only your side of the conversation is saved

• A Quarto Document is like a scrapbook with R
  • You can combine code and formatted text
  • Both sides of the conversation are saved

Arithmetic

10 + 3

[1] 13

10 - 3

[1] 7

10 * 3

[1] 30

10 / 3

[1] 3.333333

10 ^ 2

[1] 100

The four operators you already know, plus ^ for powers. Spaces are optional.

Pitfall: Notation R Does Not Accept

10 x 3

Error: unexpected symbol in "10 x"

10 \ 3

Error: unexpected '\' in "10 \"

Multiplication is *, never x, and division is /, the slash that leans the other way. R reads \ as the start of something else entirely.

Order of Operations

10 + 3 * 2

[1] 16

(10 + 3) * 2

[1] 26

Multiplication happens before addition, exactly as in algebra. Parentheses override that, and are worth adding whenever the order is not obvious.

Decimals and Negative Numbers

10 + -30

[1] -20

1.234

[1] 1.234

1 / 3

[1] 0.3333333

Negative numbers need no special treatment, and division gives a decimal, not a fraction. R prints as many digits as it thinks you need, not all it has.

How R Prints Numbers

09.870

[1] 9.87

9876543

[1] 9876543

9,876,543

Error: unexpected ',' in "9,"

R drops leading and trailing zeros that carry no information. Thousands separators are for humans: type the digits and nothing else.

Scripts

Creating a New Script

• A script is just a plain text file saved with a .R extension
  • Which makes it easy to share your code with other people
• Any one of these will create one:
  • File > New File > R Script
  • Top bar: the white square with a green plus icon
  • Ctrl+Shift+N (Win) or Cmd+Shift+N (Mac)

• A new pane appears, called the Source Editor

Entering Commands into a Script

(1.4 + 2.8 + 9.3) / 3

[1] 4.5

30.1 - 24.7

[1] 5.4

A script holds many lines at once. Think of it as drafting an email with several instructions rather than shouting one at a time.

Running One Line of Code

• Hitting Enter or Return does not run the code; it just adds a new line

• To run the line your cursor is on:
  • Click the Run button (top-right of the Source Editor)
  • Or press Ctrl+Enter (Win) / Cmd+Return (Mac)

• The results appear down in the Console

Running Many Lines of Code

• To run several lines at once:
  • Highlight them with the mouse, then click Run
  • Or highlight them and press Ctrl+Enter / Cmd+Return

• To run the whole script at once:
  • Click the Source button (top-right)
  • Or press Ctrl+Shift+Enter / Cmd+Shift+Return

Adding Comments to Scripts

# Calculate the average score on the quiz
(1.4 + 2.8 + 9.3) / 3

[1] 4.5

100 / 9 # a comment can also end a line

[1] 11.11111

Anything after a # is ignored by R and exists only for human readers. A comment can sit on its own line or at the end of one; the code still runs.

Saving the Script File

• Any one of these will do it:
  • File > Save
  • Source bar: the blue and white disk icon
  • Ctrl+S (Win) or Cmd+S (Mac)

• For now, save it wherever; we will learn about Projects soon

• You now have a .R file you can keep or transfer
  • Only the code is saved, not the results