讲解 CSE 6242 Data and Visual Analytics

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CSE 6242 / CX 4242: Data and Visual Analytics | Georgia Tech | Spring 2024
HW 2: Tableau, D3 Graphs, and Visualization
Important Notes .........................................................................................................................................2
Submission Instructions.............................................................................................................................2
Grading and Feedback ..............................................................................................................................2
Download the HW2 Skeleton before you begin .....................................................................................3
Homework Overview..................................................................................................................................3
Q1 [25 points] Designing a good table. Visualizing data with Tableau........................................................4
Setting Up Tableau ................................................................................................................................4
Connecting to Data ................................................................................................................................4
Table and Chart Design .........................................................................................................................5
Important Points about Developing with D3 in Questions 2–5.............................................................8
Q2 [15 points] Force-directed graph layout ................................................................................................9
Q3 [15 points] Line Charts .......................................................................................................................11
Q4 [20 points] Interactive Visualization ....................................................................................................16
Q5 [25 points] Choropleth Map of Board Game Ratings ..........................................................................21
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Important Notes
1. Submit your work by the due date on the course schedule.
a. Every assignment has a 48-hour grace period. You may use it without asking us.
b. Before the grace period expires, you may resubmit as many times as you need to.
c. The grace period is a lenient buffer for resolving last minute issues. We do not recommend
starting new work or modifying existing work during the grace period.
d. TA assistance is not guaranteed during the grace period.
e. Submissions during the grace period will display as "late" and will not incur a penalty.
f. We will not accept any submissions after the grace period.
2. Always use the most up-to-date assignment (version number at the bottom right of this document).
3. You may discuss ideas with other students at the "whiteboard" level (e.g., how cross-validation works,
use HashMap instead of array) and review any relevant materials online. However, each student
must write up and submit the student's own answers.
4. All incidents of suspected dishonesty, plagiarism, or violations of the Georgia Tech Honor Code will
be subject to the institute's Academic Integrity procedures, directly handled by the Office of Student
Integrity (OSI). Consequences can be severe, e.g., academic probation or dismissal, a 0 grade for
assignments concerned, and prohibition from withdrawing from the class.
Submission Instructions
Carefully read and follow the high-level instructions below, and the detailed instructions in each question.
1. Submit ALL deliverables via Gradescope. We will not accept submissions anywhere else.
2. Submit all required files, as specified at the beginning of each question. We will not grade any
submissions that deviate from the specified format (extra files, misnamed files, etc.).
3. Each submission and its score will be recorded and saved by Gradescope. By default, Gradescope
uses your last submission for grading. To use a different submission, you MUST "activate" it
(click "Submission History" button at bottom toolbar, then "Activate").
Grading and Feedback
The maximum possible score for this homework is 100 points. Students can choose to complete any 90 points
worth of work to receive 100% for this assignment, and can receive more than 100% if additional work is
submitted. For example, if a student scores 100 points, that student will receive 111% for the assignment.
We will grade all questions using the Gradescope platform. Question 1 will be manually graded after
the grace period. Questions 2-5 are auto-graded. Keep the following in mind:
1. You can access Gradescope through Canvas.
2. You may upload your code periodically to Gradescope to obtain feedback on your code. Gradescope
will auto-grade your submission using the same test cases that we use to grade your work.
3. You must not use Gradescope as the primary way to test your code's correctness, since it provides
only a few test cases, and error messages may not be as informative as local debuggers. Iteratively
develop and test your code locally, write more test cases, and follow good coding practices. Use
Gradescope mainly as a "final" check.
4. Gradescope cannot run code that contains syntax errors. If Gradescope is not running, verify:
a. Your code is free of syntax errors (by running locally)
b. All methods have been implemented
c. You have submitted the correct file with the correct name
5. Do not share links to your Gradescope submissions in public posts
6. When many students use Gradescope simultaneously, it may slow down or fail to communicate with
the tester. It can become even slower as the submission deadline approaches. You are responsible
for submitting your work on time.
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Download the HW2 Skeleton before you begin
Homework Overview
"Visualization gives you answers to questions you didn't know you have" - Ben Schneiderman
This homework focuses on exploring and creating data visualizations using two of the most popular tools in
the field. Data visualization is an integral part of exploratory analysis and communicating key insights. All
questions use data on the same topic to highlight the uses and strengths of different types of visualizations.
The data comes from BoardGameGeek and includes games' ratings, popularity, and metadata.
Below are some terms you will often see in the questions:
• Rating – a value from 0 to 10 given to each game. BoardGameGeek calculates a game's overall
rating in different ways including Average and Bayes, so make sure you are using the correct rating
called for in a question. A higher rating is better than a lower rating.
• Rank – the overall rank of a boardgame from 1 to n, with ranks closer to 1 being better and n being
the total number of games. The rank may be for all games or for a subgroup of games such as
abstract games or family games.
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Q1 [25 points] Designing a good table. Visualizing data with Tableau.
Goal Design a table, a grouped bar chart, and a stacked bar chart with filters in Tableau.
Technology Tableau Desktop
Deliverables Gradescope: After selecting HW2 - Q1, click Submit Images. You will be taken to a
list of questions for your assignment. Click Select Images and submit the following
four PNG images under the corresponding questions:
● table.png: Image/screenshot of the table in Q1.a
● grouped_barchart.png: Image of the chart in Q1.b
● stacked_barchart_1.png: Image of the chart in Q1.c after filtering data for
Max.Players = 2
● stacked_barchart_2.png: Image of the chart in Q1.c after filtering data for
Max.Players = 4 a
Q1 will be manually graded after the grace period.
Setting Up Tableau
Install and activate Tableau Desktop by following “HW2 Instructions” on Canvas. The product activation key
is for your use in this course only. Do not share the key with anyone. If you already have Tableau Desktop
installed on your machine, you may use this key to reactivate it. a
If you do not have access to a Mac or Windows machine, use the 14-day trial version of Tableau Online:
1. Visit https://www.tableau.com/trial/tableau-online
2. Enter your information (name, email, GT details, etc.)
3. You will then receive an email to access your Tableau Online site
4. Go to your site and create a workbook a
If neither of the above methods work, use Tableau for Students. Follow the link and select "Get Tableau For
Free". You should be able to receive an activation key which offers you a one-year use of Tableau Desktop
at no cost by providing a valid Georgia Tech email.
Connecting to Data
1. It is optional to use Tableau for Q1a. Otherwise, complete all parts using a single Tableau workbook.
2. Q1 will require connecting Tableau to two different data sources. You can connect to multiple data
sources within one workbook by following the directions here.
3. For Q1a and Q1b:
a. Open Tableau and connect to a data source. Choose To a File – Text file. Select
the popular_board_game.csv file from the skeleton.
b. Click on the graph area at the bottom section next to "Data Source" to create worksheets.
4. For Q1c:
a. You will need a data.world account to access the data for Q1c. Add a new data source by
clicking on Data – New Data Source.
b. When connecting to a data source, choose To a Server – Web Data Connector.
c. Enter this URL to connect to the data.world data set on board games. You may be prompted
to log in to data-world and authorize Tableau. If you haven’t used data.world before, you will
be required to create an account by clicking “Join Now”. Do not edit the provided SQL query. a
NOTE: If you cannot connect to data-world, you can use the provided csv files for Q1 in the skeleton.
The provided csv files are identical to those hosted online and can be loaded directly into Tableau. a
d. Click the graph area at the bottom section to create another worksheet, and Tableau will
automatically create a data extract.
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Table and Chart Design
a. [5 points] Good table design. Visualize the data contained in popular_board_game.csv as a data table
(known as a text table in Tableau). In this part (Q1a), you can use any tool (e.g., Excel, HTML, Pandas,
Tableau) to create the table.
a
We are interested in grouping popular games into "support solo" (min player = 1) and
"not support solo" (min player > 1). Your table should clearly communicate information about these two groups
simultaneously. For each group (Solo Supported, Solo Not Supported), show: a
1. Total number of games in each category (fighting, economic, ...)
2. In each category, the game with the highest number of ratings. If more than one game has the same
(highest) number of ratings, pick the game you prefer. NOTE: Level of Detail expressions may be useful if
you use Tableau.
3. Average rating of games in each category (use simple average), rounded to 2 decimal places.
4. Average playtime of games in each category, rounded to 2 decimal places.
5. In the bottom left corner below your table, include your GT username (In Tableau, this can be done
by including a caption when exporting an image of a worksheet or by adding a text box to a dashboard.
If you use Tableau, refer to the tutorial here).
6. Save the table as table.png. (If you use Tableau, go to Worksheet/Dashboard  Export  Image).
NOTE: Do not take screenshots in Tableau since your image must have high resolution. You can take a
screenshot If you use HTML, Pandas, etc. a
Your learning goal here is to practice good table design, which is not strongly dependent on the tool that you
use. Thus, we do not require that you use Tableau in this part. You may decide the most meaningful column
names, the number of columns, and the column order. You are not limited to only the techniques described
in the lecture. For OMS students, the lecture video on this topic is Week 4 - Fixing Common Visualization
Issues - Fixing Bar Charts, Line Charts. For campus students, review lecture slides 43 and 44.
b. [10 points] Grouped bar chart. Visualize popular_board_game.csv as a grouped bar chart in Tableau.
Your chart should display game category (e.g., fighting, economic,...) along the horizontal axis and game
count along the vertical axis. Show game playtime (e.g., <=30, (30, 60]) for each category. NOTE: Do not
differentiate between “support solo” and “non-support solo” for this question. a
1. Design a vertically grouped bar chart. For each category, show the game count for each playtime.
2. Include clearly labeled axes, a clear chart title, and a legend.
3. In the bottom left corner of your image, include your GT username. NOTE: In Tableau, this can be done
by including a caption when exporting an image of a worksheet or by adding a text box to a dashboard.
Refer to the tutorial here.
4. Save the chart as grouped_barchart.png (go to Worksheet/Dashboard  Export  Image.
NOTE: Do not take screenshots in Tableau since your image must have high resolution.
The main goal here is for you to get familiarized with Tableau. Thus, we kept this open-ended, so you can
practice making design decisions. We will accept most designs. We show one possible design in Figure
1b, based on the tutorial from Tableau.
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Figure 1b: Example of a grouped bar chart. Your chart may appear different and can earn full credit if it meets all the
stated requirements. Your submitted image should include your GT username in the bottom left.
c. [10 points] Stacked bar chart. Visualize the data.world dataset (or games_detailed_info_filtered.csv if
using the local files in the skeleton) as a stacked bar chart. Showcase the count of games in different
categories and the relationship between game categories, their mechanics, and max player size. a
1. Create a Worksheet with a stacked bar chart that shows game counts for each playing mechanic
(sub-bars) for each game category. NOTE: This data contains duplicate rows, as each row represents a
distinct game. Do not remove duplicate rows from the data.
2. Display game counts along the vertical axis and category along the horizontal axis.
3. Include clear axes labels, a clear chart title, and a legend.
4. Create a Dashboard using the worksheet you created in Step 1.
5. Add a filter for number of 'Max.Players' allowed in each game. Update the chart using this filter to
generate the following chart images (Refer to the tutorial here on how to add a filter in a dashboard.
Make sure to add 'Max.Players' in the filter shelf in the Worksheet first, like this):
a. Select "2 Players" only in the filter. Save the resulting chart as 'stacked_barchart_1.png'
b. Select "4 Players" only in the filter. Save the resulting chart as 'stacked_barchart_2.png'
c. Both images must include your GT username in the bottom left. This can be added using a
text box. Refer to the tutorial here.https://youtu.be/fRwQenvBJ6I
d. In each image, the filter must be visible. If you are using Tableau Online, you may need to
add your worksheet containing the chart to a dashboard and then download an image of the
dashboard that contains both the filter and the chart.
Note: To save a dashboard image, go to Dashboard - Export Image. Do not submit screenshots.
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a
Figure 1c: Example of a stacked bar chart after selecting "4 Players" in Max.Players filter. Your chart may appear
different and can earn full credit if it meets all the stated requirements. Your submitted image should include your GT
username in the bottom left.
Optional Reading: The effectiveness of stacked bar charts is often debated—sometimes, they can be confusing,
difficult to understand, and may make data series comparisons challenging.
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Important Points about Developing with D3 in Questions 2–5
1. We highly recommend that you use the latest Chrome browser to complete this question. We will
grade your work using Chrome v92 (or higher).
2. You will work with version 5 of D3 in this homework. You must NOT use any D3 libraries (d3*.js) other
than the ones provided in the lib folder.
3. For Q3–5, your D3 visualization MUST produce a DOM structure as specified at the end of each
question. Not only does the structure help guide your D3 code design, but it also enables your code
to be auto-graded (the auto-grader identifies and evaluates relevant elements in the rendered HTML).
We highly recommend you review the specified DOM structure before starting to code.
4. You need to setup a local HTTP server in the root (hw2-skeleton) folder to run your D3
visualizations, as discussed in the D3 lecture (OMS students: the video "Week 5 - Data Visualization
for the Web (D3) - Prerequisites: JavaScript and SVG". Campus students: see lecture PDF.). The
easiest way is to use http.server for Python 3.x. (for more details, see link).
5. All d3*.js files in the lib folder must be referenced using relative paths, e.g., "../lib/"
in your html files. For example, if the file "Q2/submission.html" uses d3, its header should contain:

It is incorrect to use an absolute path such as:

6. For questions that require reading from a dataset, use a relative path to read in the dataset file. For
example, suppose a question reads data from earthquake.csv, the path should simply be
"earthquake.csv" and NOT an absolute path such as "C:/Users/polo/hw2-skeleton/Q/earthquake.csv".
7. You can and are encouraged to decouple the style, functionality and markup in the code for each
question. That is, you can use separate files for CSS, JavaScript and html.
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Q2 [15 points] Force-directed graph layout
Goal Create a network graph shows relationships between games in D3. Use interactive
features like pinning nodes to give the viewer some control over the visualization.
Technology D3 Version 5 (included in the lib folder)
Chrome v92.0 (or higher): the browser for grading your code
Python http server (for local testing)
Allowed Libraries D3 library is provided to you in the lib folder. You must NOT use any D3 libraries
(d3*.js) other than the ones provided. On Gradescope, these libraries are provided
for you in the auto-grading environment.
Deliverables [Gradescope] Q2.(html/js/css): The HTML, JavaScript, CSS to render the
graph. Do not include the D3 libraries or board_games.csv dataset.
You will experiment with many aspects of D3 for graph visualization. To help you get started, we have
provided the Q2.html file (in the Q2 folder) and an undirected graph dataset of boardgames,
board_games.csv file (in the Q2 folder). The dataset for this question was inspired by a reddit post about
visualizing boardgames as a network, where the author calculates the similarity between board games
based on categories and game mechanics where the edge value between each board game (node) is the
total weighted similarity index. This dataset has been modified and simplified for this question and does not
fully represent actual data found from the post. The provided Q2.html file will display a graph (network) in a
web browser. The goal of this question is for you to experiment with the visual styling of this graph to make
a more meaningful representation of the data. Here is a helpful resource (about graph layout) for this
question.
Note: You can submit a single Q2.html that contains all the css and js components; or you can split Q2.html
into Q2.html, Q2.css, and Q2.js.
a. [2 points] Adding node labels: Modify Q2.html to show the node label (the node name, e.g., the source)
at the top right of each node in bold. If a node is dragged, its label must move with it.
b. [3 points] Styling edges: Style the edges based on the "value" field in the links array:
• If the value of the edge is equal to 0 (similar), the edge should be gray, thick, and solid (The dashed
line with zero gap is not considered as solid).
• If the value of the edge is equal to 1 (not similar), the edge should be green, thin, and dashed.
c. [3 points] Scaling nodes:
1. [1.5 points] Scale the radius of each node in the graph based on the degree of the node (you may try
linear or squared scale, but you are not limited to these choices).
Note: Regardless of which scale you decide to use, you should avoid extreme node sizes, which will
likely lead to low-quality visualization (e.g., nodes that are mere points, barely visible, or of huge sizes
with overlaps).
Note: D3 v5 does not support d.weight (which was the typical approach to obtain node degree in D3
v3). You may need to calculate node degrees yourself. Example relevant approach is here.
2. [1.5 points] The degree of each node should be represented by varying colors. Pick a meaningful
color scheme (hint: color gradients). There should be at least 3 color gradations and it must be visually
evident that the nodes with a higher degree use darker/deeper colors and the nodes with lower
degrees use lighter colors. You can find example color gradients at Color Brewer.
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d. [6 points] Pinning nodes:
1. [2 points] Modify the code so that dragging a node will fix (i.e., "pin") the node's position such that it
will not be modified by the graph layout algorithm (Note: pinned nodes can be further dragged around
by the user. Additionally, pinning a node should not affect the free movement of the other nodes).
Node pinning is an effective interaction technique to help users spatially organize nodes during graph
exploration. The D3 API for pinning nodes has evolved over time. We recommend reading this post
when you work on this sub-question.
2. [1 points] Mark pinned nodes to visually distinguish them from unpinned nodes, i.e., show pinned
nodes in a different color.
3. [3 points] Double clicking a pinned node should unpin (unfreeze) its position and unmark it. When a
node is no longer pinned, it should move freely again.
IMPORTANT:
1. For part 1 to consistently pass the autograder (which tests that a dragged node becomes pinned
and retains its position), you may need to increase the radius of the highly-weighted nodes and
reduce their label sizes, so that the nodes can be more easily detected by the autograder's
webdriver mouse cursor.
2. To avoid timeout errors on Gradescope, complete the double click function in part 3 before
submitting.
3. If you receive timeout messages for all parts and your code works locally on your computer,
verify that you are indeed using the appropriate ids provided in the "add the nodes" section in the
skeleton code.
4. D3 v5 does not support the d.fixed method (it was deprecated after D3 v3). For our purposes, it
is used as a Boolean value to indicate whether a node has been pinned or not.
e. [1 points] Add GT username: Add your Georgia Tech username (usually includes a mix of letters and
numbers, e.g., gburdell3) to the top right corner of the force-directed graph (see example image). The GT
username must be a element having the id: "credit"
Figure 2a: Example of Visualization with pinned node (yellow). Your chart may appear different, and can earn full
credit if it meets all the stated requirements.
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Q3 [15 points] Line Charts
Goal Explore temporal patterns in the BoardGameGeek data using line charts in D3 to
compare how the number of ratings grew. Integrate additional data about board
game rankings onto these line charts and explore the effect of axis scale choice.
Technology D3 Version 5 (included in the lib folder)
Chrome v92.0 (or higher): the browser for grading your code
Python http server (for local testing)
Allowed Libraries D3 library is provided to you in the lib folder. You must NOT use any D3 libraries
(d3*.js) other than the ones provided. On Gradescope, these libraries are provided
for you in the auto-grading environment.
Deliverables [Gradescope] Q3.(html / js / css): The HTML, JavaScript, CSS to render the line
charts. Do not include the D3 libraries or boardgame_ratings.csv dataset.
Use the dataset provided in the file boardgame_ratings.csv (in the Q3 folder) to create line charts.
Refer to the tutorial for line chart here or here.
Note: You will create four charts in this question, which should be placed one after the other on a single
HTML page, similar to the example image below (Figure 3). Note that your design need NOT be identical to
the example; however, the submission must follow the DOM structure specified at the end of this question.
IMPORTANT: use the Margin Convention guide for specifying chart dimensions and layout. The autograder
will assume this convention has been followed for grading purposes. The SVG viewBox attribute is not
recommended to define the position and dimension of your chart.
a. [5 points] Creating line chart. Create a line chart (Figure 3a) that visualizes the number of board game
ratings from November 2016 to August 2020 (inclusively), for the eight board games: ['Catan', 'Dominion',
'Codenames', 'Terraforming Mars', 'Gloomhaven', 'Magic: The Gathering', 'Dixit', 'Monopoly']. Use
d3.schemeCategory10() to differentiate these board games. Add each board game's name next to its
corresponding line. For the x-axis, show a tick label for every three months. Use D3 axis.tickFormat() and
d3.timeFormat() to format the ticks to display abbreviated months and years. For example, Jan 17, Apr 17,
Jul 17. (See Figure 3a and its x-axis ticks).
● Chart title: Number of Ratings 2016-2020
● Horizontal axis label: Month. Use D3.scaleTime().
● Vertical axis label: Num of Ratings. Use a linear scale (for this part a).
VERY IMPORTANT — Beware of “Silent Date Conversion": Opening the csv file in an application like
Excel may silently modify date strings without warning you, e.g., converting hyphen-separated date strings
(e.g., 2016-11-01) into slash-separated date strings (e.g., 11/01/16). Impacted students would see a
“correct” line chart visualization on their local computers, but when they upload their code to Gradescope,
test cases will fail (e.g., tick labels are not found, lines are not drawn) because the x-scale cannot be
computed (as the dates are parsed as NaN). To view the content of a csv file, we recommend you
only use text editors (e.g., sublime text, notepad) that do not silently modify csv files.
b. [5 points] Adding board game rankings. Create a line chart (Figure 3b) for this part (append to the same
HTML page) whose design is a variant of what you have created in part a. Start with your chart from part a.
Modify the code to visualize how the rankings of ['Catan', 'Codenames', 'Terraforming Mars', 'Gloomhaven']
change over time by adding a symbol with the ranking text on their corresponding lines. Show the symbol for
every three months, similar to the x-axis ticks in part a. (See Figure 3b). Add a legend to explain what this
symbol represents next to your chart (See the Figure 3b bottom right).
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● Chart title: Number of Ratings 2016-2020 with Rankings
c. [5 points] Axis scales in D3. Create two line charts (Figure 3c-1,2) for this part (append to the same
HTML page) to try out two axis scales in D3. Start with your chart from part b. Then modify the vertical axis
scale for each chart: the first chart uses the square root scale for its vertical axis (only), and the second chart
uses the log scale for its vertical axis (only). Keep the symbols and the symbol legend you implemented in
part b. At the bottom right of the last chart, add your GT username (e.g., gburdell3, see Figure 3c-2 for
example).
Note: the horizontal axes should be kept in linear scale, and only the vertical axes are affected.
Hint: You may need to carefully set the scale domain to handle the 0s in data.
■ First chart (Figure 3c-1)
○ Chart title: Number of Ratings 2016-2020 (Square root Scale)
○ This chart uses the square root scale for its vertical axis (only)
○ Other features should be the same as part b.
■ Second chart (Figure 3c-2)
○ Chart title: Number of Ratings 2016-2020 (Log Scale)
○ This chart uses the log scale for its vertical axis (only). Set the y-scale domain minimum to 1.
○ Other features should be the same as part b.
Figure 3a: Example line chart. Your chart may appear different, and can earn full credit if it meets all stated
requirements.
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Figure 3b: Example of a line chart with rankings. Your chart may appear different, and can earn full credit if it meets all
stated requirements.

Figure 3c-1: Example of a line chart using square root scale. Your chart may appear different and can earn full credit if
it meets all stated requirements.
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Figure 3c-2: Example of a line chart using log scale. Your chart may appear different but can earn full credit if it meets
all stated requirements.
Note: Your D3 visualization MUST produce the following DOM structure.

|
+-- chart title
|
+-- containing Q3.a plot elements
|
+-- containing plot lines, line labels
|
+-- x-axis
| |
| +-- (x-axis elements)
| |
| +-- x-axis label
|
+-- y-axis
|
+-- (y-axis elements)
|
+-- y-axis label

|
+-- chart title
|
+-- containing Q3.b plot elements
| |
| +-- containing plot lines, line labels
| |
| +-- for x-axis
| | |
| | +-- (x-axis elements)
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| | |
| | +-- x-axis label
| |
| +-- for y-axis
| | |
| | +-- (y-axis elements)
| | |
| | +-- for y-axis label
| |
| +-- containing plotted symbols, symbol labels
|
+-- containing legend symbol and legend text element(s)

(e.g., id="svg-c-1", etc.)

(e.g., id="svg-c-2", etc.)