A Tour of R

(Sections 1.2-1.6)

Arithmetic

Some Arithmetic

R can be used like a calculator:

(27-3)/10

[1] 2.4

To get \(3^2 + 4^2\) try:

3^2+4^2

[1] 25

More Arithmetic

Cube-root of 64:

64^(1/3)

[1] 4

R has a special square-root function:

sqrt(64)

[1] 8

Practice

Write one line of R-code to find:

\[\sqrt{3^2 + 4^2}\]

Variables

“Storing” a Value

a <- 10

<- is the assignment operator
it binds the name a to the value 10

Stored Value

Now you have the 10 whenever you want:

[1] 10

a + 23

[1] 33

sqrt(a)

[1] 3.162278

Descriptive Variable-Names

Information about a creature in the Land of Oz:

creatureType <-"Munchkin"
creatureName <- "Boq"
creatureFood <- "corn"

Reusing our Variables

paste("Hello, I am a ",
      creatureType,
      ". My name is ",
      creatureName,
      ".  I like to eat ",
      creatureFood,
      ".",
      sep = "")

[1] "Hello, I am a Munchkin. My name is Boq.  I like to eat corn."

About `paste()`

paste() is also a function
it “pastes” its arguments together …
… with sep stuck in between
so when sep="", nothing is in between

Observe …

Arguments for a function are separated by commas.
R basically ignores “whitespace”
including newlines
so you can spread a single command across many lines!

Whitespace Still Matters …

… inside values:

"Ted dy"

[1] "Ted dy"

100 3

## Error: unexpected numeric constant in "100 3"

Special Newline Character!

\n will make a new line:

paste("Hello, I am a ",
      creatureType,
      ".\nMy name is ",
      creatureName,
      ".\nI like to eat ",
      creatureFood,
      ".",
      sep = "")

[1] "Hello, I am a Munchkin.\nMy name is Boq.\nI like to eat corn."

Well, not when just printed!

Let’s `cat()` it, Instead

message <- paste("Hello, I am a ",
                 creatureType,
                 ".\nMy name is ",
                 creatureName,
                 ".\nI like to eat ",
                 creatureFood,
                 ".",
                 sep = "")
cat(message)

Hello, I am a Munchkin.
My name is Boq.
I like to eat corn.

Variables Upon Variables!

a <- 10
b <- 27
mySum <- a + b
mySum

[1] 37

Functions

Reusing Your Code

In order to re-use a useful bit of code, make a function out of it:

intro <- function(name, type, food) {
  message <- paste("Hello, I am a ",
                 type,
                 ".  \nMy name is ",
                 name,
                 ".\nI like to eat ",
                 food,
                 ".",
                 sep = '')
  cat(message)
}

This defines a function called intro().

Using our Function

To use a function, call it:

intro(name = "Frederick", type = "Winkie", food = "macaroni")

Hello, I am a Winkie.  
My name is Frederick.
I like to eat macaroni.

Parameters and Arguments

Parameters are names that you use inside the body of the function
Arguments are the values you assign to the parameters when you call the function

Parameter	Argument
`name`	“Frederick”
`type`	“Winkie”
`food`	“macaroni”

You Can Be Lazy

You can skip the names of the parameters:

intro("Frederick", "Winkie", "macaroni")

Hello, I am a Winkie.  
My name is Frederick.
I like to eat macaroni.

But you must keep the arguments in the order of the parameters you want to assign them to.

Data and Graphics

A Contributed Package

mosaicData is a contributed R-package
It contains some datasets that are interesting and useful

Let’s attach this package:

library(mosaicData)

Births78

help("Births78")

Births78 is a data frame.
data frames are an important kind of data structure in R

Data Structure

A particular way of organizing information in a computer program so that it can be used efficiently.

Take a Peek

head(Births78, n = 10)

         date births wday year month day_of_year day_of_month day_of_week
1  1978-01-01   7701  Sun 1978     1           1            1           1
2  1978-01-02   7527  Mon 1978     1           2            2           2
3  1978-01-03   8825  Tue 1978     1           3            3           3
4  1978-01-04   8859  Wed 1978     1           4            4           4
5  1978-01-05   9043  Thu 1978     1           5            5           5
6  1978-01-06   9208  Fri 1978     1           6            6           6
7  1978-01-07   8084  Sat 1978     1           7            7           7
8  1978-01-08   7611  Sun 1978     1           8            8           1
9  1978-01-09   9172  Mon 1978     1           9            9           2
10 1978-01-10   9089  Tue 1978     1          10           10           3

More of a Peek

View(Births78)

Research Question

Does the daily number of births vary with time of year?

Making a Graph

Expand to see code

ggplot(Births78, aes(x = date, y = births)) + 
  geom_point() +
  labs(
    x = "Day of the Year",
    y = "Number of U.S. Births",
    title = "Birth-Numbers Vary Seasonally"
  )

Interactive Graphs

A Network Graph

Code

## source:  https://r-graph-gallery.com/network-interactive.html
# Libraries
library(igraph)
library(networkD3)

# create a dataset:
data <- data.frame(
  from=c("A", "A", "B", "D", "C", "D", "E", "B", "C", "D", "K", "A", "M"),
  to=c("B", "E", "F", "A", "C", "A", "B", "Z", "A", "C", "A", "B", "K")
)

# Plot
p <- simpleNetwork(data, height="400px", width="400px")

p

Playing Games!

“All work and no play makes Jack a dull boy.”

Wordle

library(wordler)

play_wordler()