HW3 Theory: Marks and Channels


The purpose of this assignment is to provide you with some experience evaluating the use of mark embellishments within visualizations. You will also gain some familiarity using Processing to create more marks and connect them to data attributes through channels. This assignment must be completed on your own. Each part is equally weighted: please follow the submission guidelines on T-Square to receive full credit.


Part 1: Written Report (1-2 pages)

Below is a link to a recently published academic paper that describes a series of experiments on mark embellishments. Read the paper and write a report explaining the underlying research question, the approach taken by the authors, and your personal response to the results of the experiment. Your goal here is to perform an abstract analysis of a research effort using the approaches described in the text and in class.

Your report should consist of three sections on one or two pages. First, describe the underlying research question(s) in your own words. Why perform this research? What's the impact for the potential outcomes? What principles have we covered in class that relate to the research questions? Second, describe the approach taken by the authors to find answers. What level of validation would this be considered? How does this approach compare to the approach taken in papers we have discussed in class (e.g, the Mechanical Turk paper by Heer et al.), and how does it compare to alternative forms of validation? Third, discuss your personal response to the results obtained by the authors. Are you convinced by what they found? Do you have any objections to their findings, and if so, why? Are there any counterexamples of visualizations that you believe refute their claims?

Grading: We will evaluate the quality of your analysis of the paper within each section. We will evaluate if you followed the directions and estimate the quality of your conclusions. We will evaluate how well you justify your conclusions based upon the material we've covered in class so far. Please proofread your submission before submitting it and make sure it is free of spelling and grammar issues.

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Part 2: Software

You are going to write a sketch capable of visually representing product sales data. The data consists of a list of sales figures of coffee types over time. This is a much smaller data set than you used in the previous assignment, but there are still some careful steps you need to take when aggregating the data. You are going to write a sketch that generates bar charts of the coffee sales over time, similar to the chart in the image below. In addition to the standard rendering strategy for bar charts, you will also be implementing the embellished bar charts described in the paper for Part 1.

Your system must support the following capabilities:

Most of the information required for this assignment can be found in the Processing reference. The interactive components (e.g., buttons, dropdown menus) will be made much easier if you employ an existing library such as controlP5, though you cannot use such a library to render your chart. Please provide all of your code in a single sketch directory named "barVis" that you submit. This directory must include a file named "barVis.pde" with setup() and draw() functions so that we can run it.

Grading: Your assignment will be graded on whether it can perform the list of capabilities correctly. Each capability will be worth one fifth of the grade for this part of the homework. The extra credit mentioned in the descriptions are each worth one tenth of the of the grade for this part of the homework (half the value of getting the primary functionality correct). Feel free to attempt any, or all, of the extra credits but please target the primary functionality first. If your code does not compile, we cannot give you any credit for the software portion of this assignment.

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Paper

Drew Skau, Lane Harrison, Robert Kosara, An Evaluation of the Impact of Visual Embellishments in Bar Charts, Computer Graphics Forum (Proceedings EuroVis), vol. 34, no. 3, pp. 221–230, 2015. [pdf]

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Data Set

Coffee Sales Two Year Set [csv]

The csv file contains data items with eight attributes in comma-separated-value format. The data file has column headers, so the data should be relatively self explanatory. Do not treat date as an ordinal attribute for the height of the bars. You may, however, use year or month as categorical attributes for the bar identity (this is not a requirement).

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