---
title: 'DS 2020 - Summer 2025 - Homework #2'
author: "Your Name"
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

# Lab: Ames Housing Data Exploration

## Overview

In this lab, you will explore the `ames` dataset from the `classdata` package, which contains residential sales data in Ames, Iowa since 2017. All work should be completed in this `.Rmd` file and submitted through Canvas.

The main variable of interest is `Sale_Price`. You will:

-   Investigate this variable and its distribution
-   Identify and explore one other variable that may relate to `Sale_Price`
-   Use code, visualizations, and written explanation to communicate your findings

Make sure your `.Rmd` file knits cleanly to `.html`. You will submit both the `.Rmd` and the knitted output.

## Step 1: Data Exploration

1.  Inspect the first few lines of the data set:
    -   What variables are there?
    -   Of what type are the variables?
    -   What does each variable mean?
    -   What do you expect their data ranges to be?
    
> answer

2.  Begin the exploration with the main variable, `Sale_Price`:
    -   What is the range of this variable?
    -   Create a histogram to visualize the distribution.
    -   What is the general pattern? Are there any unusual or extreme values?
    
> answer

3.  Choose a second variable that may relate to `Sale_Price`:
    -   What is the range of this variable? Plot it and describe the pattern.
    -   Explore the relationship between this variable and `Sale_Price`. Use a scatterplot, boxplot, or faceted bar chart—whichever is most appropriate.
    -   Describe the pattern. Does this second variable help explain anything you observed in `Sale_Price`?
    
> answer

# Homework Assignment

## Chick Weights

The `ChickWeight` data set is part of the base package `datasets`. See `?ChickWeight` for details on the data. For all of the questions use `dplyr` functions whenever possible.

1.  Download the RMarkdown file with these homework instructions to use as a template for your work. Make sure to replace "Your Name" in the YAML with your name. To get full points, show your R code (in a code chunk) and write answers to the questions.

2.  What variables are part of the dataset?

> answer

3.  Get a frequency breakdown of the number of chicks, their average weight and the standard deviation of the weights in each of the diets at the start of the study.

- extra credit: construct a ggplot that shows average weights by diet with an interval (shown as a line) of +- the standard deviation around the averages. (Hint: read this article regarding [ggplot error bars](http://www.sthda.com/english/wiki/ggplot2-error-bars-quick-start-guide-r-software-and-data-visualization))

> answer

4.  Each chick should have twelve weight measurements. Use the `dplyr` package to identify how many chicks have a complete set of weight measurements and how many measurements there are on average in the incomplete cases. Extract a subset of the data for all chicks with complete information and name the data set `complete`. (Hint: you might want to use mutate to introduce a helper variable consisting of the number of observations)

> answer

5.  In the complete data set introduce a new variable that measures the current weight difference compared to day 0. Name this variable `weightgain`. (Hint: use mutate and `?mutate` to check the parameter `.by`. This parameter can create a temporary `group_by` so that we can do calculation in each subgroup, i.e. for each combination of chick and diet, `weight - min(weight)`)

> answer

6.  Use `ggplot2` to create side-by-side boxplots of `weightgain` by `Diet` for day 21. Describe the relationship in 2-3 sentences. Change the order of the categories in the Diet variable such that the boxplots are ordered by median `weightgain`.

> answer

Note: Your submission is supposed to be fully reproducible, i.e. the TA and I will 'knit' your submission in RStudio.

For the submission: submit your solution in an R Markdown file and (just for insurance) submit the corresponding html (or Word) file with it.

(Optional but encouraged):  
If you’d like to practice using GitHub, feel free to push your `.Rmd` and knitted `.html` file to a **public GitHub repository** under your own account. If you do, paste the link to your GitHub repo below:

> GitHub repo link (optional): `__________`