Problem set 1

1 Instructions/Setup

Download source

  • Make sure you have a GitHub account. In your GitHub account, create a GitHub repository named STAT3000.

  • Create an RStudio Project, e.g., stat3000, connected to the GitHub repo (clone or connect existing).

  • Answer each item inside this Quarto file. Show commands/code where requested.

2 Tasks

  1. Project folders
    In your project root, create the folders: hw/, img/, data/, code/, docs/.
    Provide either:

    • the Unix commands you used, or
    • the R commands you used
    # Your commands here

  2. RStudio project + Quarto document
    Create a Quarto document named hw1.qmd (this file).
    Include a screenshot of your RStudio session showing:

    • Files pane (project structure)
    • Git pane (if available)

  3. GitHub + repo setup
    In your Quarto document, include:

    • the repo URL
    • a screenshot showing the repo page on GitHub

  4. Create and include a plot image
    Create a simple plot in R (any plot you like), save it as img/plot.png, and include it below.

    
  # Example idea (you can change it):
  # png("img/plot.png", width = 800, height = 500) #open png device 
  # plot(cars)
  # dev.off() # close the device

  1. Define a function and compute real roots In this document, define coefficients \(a=2\), \(b=-5\), \(c=-3\). Consider \(f(x) = ax^2 + bx + c\). Print the real solutions of \(f(x)=0\) (if any).

    • If the discriminant is negative, print a message like "No real roots".
    
  # a <- 2
  # b <- -5
  # c <- -3
  # 
  # disc <- b^2 - 4*a*c
  # disc

  # Your code here to print only real roots

  2. Graph the quadratic on a specified interval Make a graph of \(f(x)\) versus \(x\) for \(x \in (-6, 6)\). Add:

    • a horizontal line at \(y = 0\)
    • points for the real roots (if they exist)
    # x <- seq(-6, 6, length.out = 400)
# fx <- a*x^2 + b*x + c

# Hint: use plot(x, fx, type="l") and abline(h=0)

  3. Write coefficients to a text file using Unix Use Unix to create a file data/coefs.txt containing a single line with:

    2 -5 -3

    Show the Unix commands you used:

    # Your commands here

  4. Copy the Quarto file using Unix Use Unix to copy hw1.qmd into code/ and name it quadratic.qmd. Show the Unix command(s):

    # Your commands here

  5. Read coefficients from file using a relative path

    Edit code/quadratic.qmd so it reads a, b, c from data/coefs.txt using a relative path. In this document, show the R code you used (it should also appear in quadratic.qmd).

    # Your code here (example outline):

# coefs <- scan("data/coefs.txt") #read numbers/string and return a vector

# a <- coefs[1]; b <- coefs[2]; c <- coefs[3]

# then compute real roots again

  6. Switch to an absolute path and test portability

    In code/quadratic.qmd, replace the relative path with: file.path(getwd(), "data/coefs.txt") Render it once to confirm it works.

    Then move the entire project folder to a new folder name (e.g., RtmpXXXX). Re-render code/quadratic.qmd. Does it still render? Briefly explain what happened, then switch back to a relative path and confirm it renders again.

  7. Render to PDF and publish to GitHub Pages-style docs folder

    Render a PDF version of hw1.qmd (or code/quadratic.qmd) and place the PDF into docs/. Show the terminal command(s) you typed:

    # Your command here. This shuold be run in a Linux terminal. 
# This command assumes your current directory is the parent directory containing `hw/hw1.qmd`. Otherwise, make appropriate change to the path to hw1.qmd
#install any missing packages on the fly

quarto render hw/hw1.qmd --to pdf  
cp hw/hw1.pdf docs/

  8. Git workflow Make at least three commits with meaningful messages, such as:

  • Add initial project structure

  • Add quadratic root computation

  • Add rendering output to docs

    In this document, paste the output of:

    git log --oneline --decorate -n 5
  1. Push to GitHub Push your work to GitHub. In this document, include:
  • a screenshot of your GitHub repo showing the folders img/, data/, code/, docs/
  • the link to the rendered PDF file in your repo (if applicable)

3 Submission checklist