Description
Instructions
In this assignment you will create a trellis scatterplot. The trellis display consists of 4 charts, each showing **real estate data for 4 cities.** Your submission should create a web page that looks like this:
You will use the dataset at `./data/real_estate.csv` to create the trellis display. Here is a snippet of the dataset:
| `location` |`beds`|`bath`|`price` |`year_built`|`sqft`|`price_per_sqft`|
|—————|——|——|———|————|——|—————-|
| New York | 2 | 1 | 999000 | 1960 | 1000 | 999 |
| New York | 2 | 2 | 2749502 | 2006 | 1418 | 1939 |
| San Francisco | 2 | 1 | 875448 | 1908 | 1158 | 756 |
| Boston | 3 | 2 | 1605468 | 1911 | 1588 | 1011 |
| Boston | 3 | 2 | 1514496 | 1924 | 1536 | 986 |
For those interested, [the NY & SF portion of this dataset](https://github.com/jadeyee/r2d3-part-1-data) comes from the [r2d3 – A visual introduction to machine learning](http://www.r2d3.us/visual-intro-to-machine-learning-part-1/) storytelling visualization. Take a look, the authors use beautiful animations and transitions to explain ML classification.
Back to the matter at hand – you will use this dataset to create the above trellis scatterplot. First, you will need to group or nest the dataset by the `location` data attribute [`San Francisco`, `New York`, `Boston`, `Philadelphia`]. Like in **Program Assignment 1**, you will need to re-configure the data for the `location` data attribute.
For this assignment, you are **required to accomplish this with the d3.nest() function.** Hopefully, you mastered it in [Program Assignment 1](https://github.gatech.edu/CS4460-Spring2018/Homework/tree/master/01_bar_chart) and during [Lab 5](https://github.gatech.edu/CS4460-Spring2018/Labs/tree/master/05_lab).
Then you will need to create each 4 trellis plots and lay them out in a uniform way. You are **required to create the trellis plot by properly using svg grouping and nested selection with d3.** See below for more details of the requirement. Look to [Lab 5](https://github.gatech.edu/CS4460-Spring2018/Labs/tree/master/05_lab) and its additional readings to understand how to accomplish nested selections and grouping.
> Reminder that this is an individual assignment. The code you turn in should be your own creation. You are certainly welcome to seek assistance from the TAs as you work on the assignment, however.
Starter code
All of the starter code for the Programming Assignments can be found at the [HW Github Repository](https://github.gatech.edu/CS4460-Spring2018/Homework). `git clone` this repository for this assignments starter code. You will need to `git pull` for all future starter code.
**You are required to use the starter code for all programming assignments.**
What to turn in
You will submit your code via T-Square. Compress your code (the `02_trellis_scatterplot` directory) into a zip file. Upload and submit this zip file via T-Square.
Deadline
Your zipped code should be submitted to T-Square by **11:55 pm on Friday March 16th**
Grading
This assignment will be graded out of a 100 point scale. If your D3 code does all of the following you will receive all 100 points:
1. Creates a trellis scatterplot with 4 subplots (in a 2 x 2 block layout) that show the required data from the instructions – we will check to make sure the subplots are data accurate.
2. Your code processes the raw data to create a nested data structure for the trellis plot. `d3.nest()` is required to accomplish this – you will lose points if you do not use `d3.nest()`.
3. You are required to add axes and label them for all subplots. You are required to label the city for all subplots.
4. You created a trellis scatterplot, and not just 4 separate scatterplots. **This requires that all subplots use the same scales.**
5. **You created the trellis plot by properly using grouping and nested selection.** In particular, to create the four subplots, you should first create four `<g>` elements within your svg, and then append data points, axes, and labels to all four `<g>` elements together. In both steps, you should use d3 data-binding and work on d3 selections (by calling methods like `selectAll()`, `data()`, and `append()`). Again, refer to [Lab 5](https://github.gatech.edu/CS4460-Spring2018/Labs/tree/master/05_lab) and its readings for examples and explanations.
6. The data points have two colors, representing the number of bedrooms (<= 2 or > 2). We leave it up to you to choose the specific colors.
7. Your plot has a legend that shows what the two colors represent. The starter code includes a legend for you. You can leave it as is, but you are also free to change its format, style and position.
You will **not** lose points on any of the following:
1. The styling of the charts, axes or labels
2. The colors you decide to use
3. The spacing or width of the subplots
4. The order of the subplots
5. Handling any other datasets than `./data/real_estate.csv`
6. The position/form of the legend
7. Conventions or legibility of your code (However, we strongly encourage you to follow the general practices for writing readable code, such as having a meaningful naming scheme and adding comments where appropriate.)
**Extra Credit (5 points)**
The above screenshot contains redundant axis labels in the trellis plot. Think about better design principles for a trellis plot we have discussed in class, and modify the axis labels in your submission to reflect a better design.
Please note that making those design modifications should not prevent you from using proper grouping and d3 selections to create the graph components. You should make sure all the requirements above are met and then make changes on top of that.
