Introduction to R

2025-02-25

Rick Gilmore

Prelude

Galileo’s head was on the block. His crime was looking up for truth…

IndigoGirlsVEVO (2009)

Overview

In the news

Ferrell (2025)

Announcements

Last time…

What I’m saying

  • Can’t & shouldn’t hide from controversy
    • Seek light and truth
  • Don’t all have to agree
  • Should (I hope) agree to continue to debate & discuss
  • Seek out, but not require agreement
  • Be courageous, not cowardly

Today

  • Why R we doing this?
  • Getting started with DataCamp

Why R we doing this?

Why learn R?

  • It’s fun
  • It’s free
  • Amaze your friends; dazzle your rivals
  • Powerful, especially for manipulating, plotting, and analyzing data
  • It will make you a more productive researcher
  • Practical job-related skill

Why should psychologists learn R?

  • R designed for data manipulation, analysis, & visualization
  • Script (program) many stages of your workflow
  • Programming reinforces analytical problem solving skills (algorithmic thinking)
    • Do this 1st
    • Do this 2nd…
  • Reproducible == robust, easy to share with others

What if I want to learn another programming language?

  • Awesome! Go for it!
  • Easier or more poetic to say some things in some languages than in others.
  • Python, Matlab, *nix shell programming, HTML/CSS/JavaScript, SQL, C/C++, and Java

RStudio

Console

  • Talk to R
  • Get a reply
Code 
license()

This software is distributed under the terms of the GNU General
Public License, either Version 2, June 1991 or Version 3, June 2007.
The terms of version 2 of the license are in a file called COPYING
which you should have received with
this software and which can be displayed by RShowDoc("COPYING").
Version 3 of the license can be displayed by RShowDoc("GPL-3").

Copies of both versions 2 and 3 of the license can be found
at https://www.R-project.org/Licenses/.

A small number of files (the API header files listed in
R_DOC_DIR/COPYRIGHTS) are distributed under the
LESSER GNU GENERAL PUBLIC LICENSE, version 2.1 or later.
This can be displayed by RShowDoc("LGPL-2.1"),
or obtained at the URI given.
Version 3 of the license can be displayed by RShowDoc("LGPL-3").

'Share and Enjoy.'

Painful lesson #1

Computers are super-literal. They are anally literal. More anally literal than any human being you’ve ever had to deal with.

You’re not going to change them. Being this anal is their superpower.

Just deal.

Parts of console

  • Prompt (>); cursor (|)
  • History of conversation via up/down arrows
  • Enter a command, then hit enter or return to say it to R
Code 
sum(1, 4, 7)
[1] 12

Functions

  • Tell the computer to do something
  • FUNCTION_NAME: what to do
  • ARGUMENTS: what to do it to/on and how
  • sum: function name
  • (1, 4, 7): arguments/inputs
    • Parentheses are like open hands giving the function something it wants
Code 
mean(1, 4, 7)
[1] 1
Code 
mean(c(1, 4, 7))
[1] 4
Code 
sum(1, 4, 7)/3
[1] 4

Code 
sort(4, 1, 7)

Getting help

sort() again

Code 
sort(c(4, 1, 7))
[1] 1 4 7

The c() command/function

  • Concatenates or Combines items into a single thing
Code 
c(4, 1, 7)
[1] 4 1 7
Code 
c(1:15)
 [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15

Assignments

Code 
my_age <- 61 # My age. Beats the alternative, I guess.

# Text that is preceded by the # character is called a comment.
# These are 'notes' you can keep about your code so you remember why you
# did something. Here, R ignores the part after the #: ' Rick's age'

Assignments (continued)

  • Give (assign) number (61) a useful/informative name (my_age)
  • Leftward arrow (<-) (option/alt + minus): assignment command
Code 
your_age <- 21
your_shoe_size <- 8.5

your_age + your_shoe_size
[1] 29.5
Code 
your_shoe_size/your_age
[1] 0.4047619

Don’t use =, use <-

  • You can substitute = but don’t. Use <-.
  • It’s stylistic, but style matters.
  • It’s like saying ‘like’ all the time. Like people will like understand you, but they’ll wonder why you like say like all the time when you really need not.
  • It’s also a topic that could get you in a ‘flame war’.
  • Avoid flame wars if you can. Life is too short.

Asking questions

  • comparison operators (==, !=, >, <, etc.).
Code 
1 == 0
[1] FALSE
Code 
sqrt(9) < 4
[1] TRUE
Code 
'rick' == 'rick'
[1] TRUE
Code 
'richard' > 'rick' # 'h' < 'k'
[1] FALSE
Code 
'richard' != 'rick'
[1] TRUE

What can we talk to R about?

  • Strings (sequences of letters, numbers, characters)
Code 
c('w', 'x', 'y', 'z')
[1] "w" "x" "y" "z"
Code 
middle_letters <- c('m', 'n', 'o')

What can we talk to R about?

  • numbers
    • 3.14159
    • 4^2
    • 1e3

What can we talk to R about?

  • data sets
  • plots
  • analyses
Code 
rand_x <- rnorm(100)
rand_y <- rnorm(100)
my_plot <- plot(rand_x, rand_y) # Give the plot a name
Code 
my_plot # Show the plot
NULL

Rules for naming things

  1. Replace spaces (and hyphens/minus characters -) with underscores (_), and
  2. Start names with letters, not numbers.
  • acceptable names for things: bigly, good_name, a_longer_good_name, Good_name1, and even thisIsCamelCaseNoUnderscores
  • unacceptable names: !good, bad name (has a space) or 1_very_bad_name (starts with a number).

Getting started with DataCamp

Sign in

Next time

Communicating uncertainty and risk

Resources

References

Ferrell, J. (2025, February 10). January was coldest in U.S. Since 1988 but globe was warmest ever. Retrieved February 17, 2025, from https://www.accuweather.com/en/climate/january-was-coldest-in-u-s-since-1988-but-globe-was-warmest-ever/1743438
IndigoGirlsVEVO. (2009). Indigo girls - galileo (official video). Youtube. Retrieved from https://www.youtube.com/watch?v=dI1keSSwdcI