In thisisdaryn/workshop:

options(htmltools.dir.version = FALSE)
knitr::opts_chunk$set(fig.align="center", fig.width=5, fig.height=5, warning = FALSE, message = FALSE)

library(xaringanthemer)
duo_accent(
  primary_color = "ivory",
  secondary_color = "midnightblue",
  header_font_google = google_font("Roboto", "400"),
  text_font_google   = google_font("Lato", "300"),
  code_font_family = "Fira Code",
  code_font_url = "https://cdn.rawgit.com/tonsky/FiraCode/1.204/distr/fira_code.css",
  header_color = "#f54278",
  title_slide_text_color = "#354a66"
)

---

What are functions?

function: reusable code that performs a well-articulated task

--

--

What types of task:

--

• return a value e.g. max gives the largest of a set of values

--

• other actions e.g. plot creates graphs

---

How to use

• calling functions, use the function name followed by ()

--

• arguments: the inputs to functions

  • placed inside the ()

  • some arguments may be mandatory; others optional

--

• get help by using ? before function name. Help page will show in the help window.

?plot

---

Where do you get functions

We can think of 3 sources of functions:

--

• built-in to R e.g. plot, max, table, summary

--

• installed via packages

--

• you can write your own

---

What is a package?

A package: is a collection of functions and data.

Some examples:

• ggplot2: a package with graphical functions

• dplyr and tidyr: packages for data wrangling

• caret: a package for machine learning

• data.table: a package for making operations with extremely large data sets fast

---

CRAN

Comprehensive R Archive Network (CRAN): The official repository of packages for the R language.

knitr::include_graphics("images/CRANScreen.png")

---

Installing and using packages

• install.packages

  • only needs to be run once to install the package.

  • gets the package from the Comprehensive R Archive Network (CRAN)

Example: Installing the genius package

install.packages("genius")

---

library: gives you access to the functions and data of a package that is already installed

Example:

First try to use the genius_lyrics function of the genius package:

sg <- genius_lyrics(artist = "Kes", song = "Savannah Grass")

--

Now use library:

library(genius)
sg <- genius_lyrics(artist = "Kes", song = "Savannah Grass")

---

sg

reactable::reactable(sg)

---

Writing our own functions

Write a function th * input: * a vector of variables * a number n

• action: identifies the n most common values in the list

---

What are the steps?

• Calculate the counts of

• Sort the counts

• Identify the n most common

• return the identified values

---

Do these steps correspond to functions we are familiar with?

• Calculate the counts of

  • we can use table

• Sort the counts

  • we can use sort

• Identify the n most common

  • subsetting

• return the identified values

thisisdaryn/workshop documentation built on Jan. 17, 2020, 7:31 p.m.