Assignment 6: R Functions and Packages

Author

Matthew DeHaven

Due

March 4, 2024

Modified

March 31, 2024

1 Accept Assignment on Github Classroom

  1. Accept Assignment 6 on Github Classroom.

  2. Clone this assignment to your computer.

  3. Initialize renv

2 Start a New Github Repository

You are going to make an R package that you are going to save and store on Github.

  • Make a new Github repository, with the name you want for your package
    • Make sure it’s public
    • You could name it “testPackage” if you would like1
  • Clone this new repository to your computer.

1 For R package names, avoid using special characters like “-” and “_” and spaces.

I am going to assume in these instructions that you named the package “testPackage”, but obviously if you named it something else, just replace the name.

3 Setup Your Package

  • Open up your local “testPackage” folder

  • Install “devtools”

  • In the terminal, run usethis::create_package(".")

This will create the package files in the current folder.

  • Add a new R script called “myfunc.r” to the “R/” folder

  • Add the following code to that script:

testPackage/R/myfunc.r
#' My first function
#'
#' @param a A numerical vector.
#' @param b Also a numerical vector.
#'
#' @return A numerical vector of a + b * a.
#' @export
#'
#' @examples
#' myfunc(3, 5)
myfunc <- function(a, b) {
  result <- a * b + a
  return(result)
}

  • In the terminal, run devtools::document()

  • Add a license by running usethis::use_mit_license() in the terminal

  • Commit all the files, and push to Github

4 Install and Load Your Package

Now, we are going to see how we can use this package in other projetcs.

  • Switch to a VS Code window with the “assignment-6” repository open

Since you made your package public on your Github account, you can install it using renv.

  • Install your package, renv::install("yourGithubUsername/testPackage")

  • Check to see if the following code works:

library(testPackage)
myfunc(3, 5)

  • Can you access the help file for your function?

  • Check to see if you can see “testPackage” in the “renv/” folder.

5 Assignment Tasks

5.1 New Functions

Estimating Beta

The task here is to write a new function to estimate \(\beta\) for a linear regression:

\[ y = \beta X + \epsilon \] \[ \Rightarrow \hspace{1cm} \widehat{\beta} = [X^\prime X]^{-1} X^\prime Y \]

Where \(y\) is a vector of \(n\) observations, \(X\) is a \(nxk\) matrix of \(k\) variables, and \(\beta\) is a vector of \(k\) variables.

  • Write a function estimate_beta()
    • takes as inputs “y” and “X”
    • returns “beta_hat”

Custom Theme

Write a function that retuns your favorite ggplot2 theme.

You’ll need to use usethis::use_package("ggplot2") to add ggplot2 as a dependency. You may possibly need to add other packages if you want to use one of their themes as a starting point.

You should make at least 3 adjustments to a default theme.

  • Write a function my_theme()
    • returns your ggplot2 theme

Document, Check, and Push

  • Make sure to document your new functions

  • Run devtools::check() and see if you get any errors or warnings, try to fix them.

  • Push your package to Github

5.2 Using Your New Functions

Now you will use the functions you have written.

In your assignment folder,

  • Re-install your “testPackage” and load it.

Check estimate_beta()

  • Add the following code to your project, and run it to check your estimate_beta() function.
y <- iris[, "Sepal.Length"] |> as.matrix()
X <- iris[, c("Sepal.Width", "Petal.Length", "Petal.Width")] |> as.matrix()

estimate_beta(y, X)
                   [,1]
Sepal.Width   1.1210617
Petal.Length  0.9235289
Petal.Width  -0.8956758
  • Compare this to the official lm() coefficients
lm(Sepal.Length ~ 0 + Sepal.Width + Petal.Length + Petal.Width, data = iris)

Call:
lm(formula = Sepal.Length ~ 0 + Sepal.Width + Petal.Length + 
    Petal.Width, data = iris)

Coefficients:
 Sepal.Width  Petal.Length   Petal.Width  
      1.1211        0.9235       -0.8957

The “0” in the formula causes lm() to not include an intercept.

Check my_theme()

  • Add your theme to the following ggplot2 code
library(ggplot2)
p <-
  iris |>
  ggplot(aes(
    x = Sepal.Length,
    y = Sepal.Width
  )) +
  geom_point()
p

  • Save your plot to a PDF called “myplot.pdf”

6 Submit Your Assignment

  • Please add a link to your “testPackage” Github repository to the assignment’s README.md file.

  • Commit all your changes to the assignment repository and push it