Week 1: Introduction to R

Introduction to Computer Programming for Data Analysis I

Tom Paskhalis

27 April 2022

Overview

• Backstory
• RStudio
• R Script
• Markdown/R Markdown
• Operators

R background

Source: University of Auckland, R Project

• S (for statistics) is a programming language for statistical analysis developed in 1976 in AT&T Bell Labs
• Original S language and its extention S-PLUS were closed source
• In 1991 Ross Ihaka and Robert Gentleman began developing R, an open-source alternative to S

R release names (v. 4.1.1 -- "Kick Things")

Source: Twitter
Extra: More on historical R release names

Popularity of Data Analysis Software

Source: SPSS is dying. R is surging.

R and development environments

• There is some choice of integrated development environments (IDEs) for R (StatET, ESS, R Commander)
• However, over the last decade RStudio became the de factor standard IDE for working in R
• You can also find R extensions for your favourite text editor (Atom, Sublime Text, Visual Studio Code, Vim)

RStudio

R Script

• Usually you want to have a record of what analysis was done and how you did it.
• So, instead of writing all your R commands in the interactive console,
• You can create an R script, write them there and run then together or one at a time.
• R script is a file with .R extension and contains a collection of valid R commands.

R Markdown

• Markdown:
  • Easy-to-read and easy-to-write plain text format;
  • Separates content from its appearance (rendition);
  • Widely used across industry sectors and academic fields;
  • .md file extension.
• RMarkdown:
  • Allows combining of R commands with regular text;
  • Compiles into PDF/DOC/HTML and other formats;
  • Can be converted into slide deck or even website!
  • .Rmd file extension

Extra: Ch 27: R Markdown in Wickham & Grolemund 2017

Markdown formatting basics

• Use _ or * for emphasis (single - italic, double - bold, triple - bold and italic)
  • *one* becomes one, __two__ - two and ***three*** - three
• Headers or decreasing levels follow #, ##, ###, #### and so on
• (Unordered) Lists follow marker -, + or *
  • Start at the left-most position for top-level
  • Indent four space and use another marker for nesting like here
• (Numbered) Lists use 1. (counter is auto-incremented)
• Links have syntax of [some text here](url_here)
• Images similarly: ![alt text](url or path to image)

R Markdown example

Some text in *italic* and **bold**

Simple list:

- A
- B

Ordered list:

1. A
1. B

Example, where $Y = X + 5$

```{r}
x <- 3
y <- x + 5
y
```

R Markdown example

Some text in italic and bold

Simple list:

• A
• B

Ordered list:

1. A
2. B

Example, where $Y = X + 5$

{r}
x <- 3
y <- x + 5
y

R basics

• R is an interpreted language (like Python and Stata)
• It is geared towards statistical analysis
• R is often used for interactive data analysis (one command at a time)
• But it also permits to execute entire scripts in batch mode

print("Hello World!")

[1] "Hello World!"

Operators

Key operators (infix functions) in R are:

• Arithmetic (+, -, *, ^, /, %/%, %%, %*%)
• Boolean (&, &&, |, ||, !)
• Relational (==, !=, >, >=, <, <=)
• Assignment (<-, <<-, =)
• Membership (%in%)

Basic mathematical operations in R

1 + 1

[1] 2

5 - 3

[1] 2

6 / 2

[1] 3

4 * 4

[1] 16

## Exponentiation, note that 2 ** 4 also works, but is not recommended
2 ^ 4

[1] 16

Advanced mathematical operations in R

# Integer division
7 %/% 3

[1] 2

# Modulo operation (remainder of division)
7 %% 3

[1] 1

Basic logical operations in R

3 != 1 # Not equal

[1] TRUE

3 > 3 # Greater than

[1] FALSE

FALSE | TRUE # True if either first or second operand is True, False otherwise

[1] TRUE

F | T # R also treats F and T as Boolean, but it is not recommended due to poor legibility

[1] TRUE

3 > 3 | 3 >= 3 # Combining 3 Boolean expressions

[1] TRUE

Next

• Introduction to computation