Heads up! To view this whole video, sign in with your Courses account or enroll in your free 7-day trial. Sign In Enroll

Data Visualization Foundations

Well done!

You have completed Data Visualization Foundations!

Sign up for Treehouse Back to Library

Pie charts

4:15 with Anwar Montasir

A pie chart shows how the total amount is divided into parts. The size of each slice indicates a proportion of the whole. You can imagine this as a literal pie. If I cut a pie into six equal slices and eat one of them, we’re left with a visual representation of how much of the pie has been eaten–that’s one-sixth of the total pie–and the five-sixths of the pie that remains.

Vocabulary

What is a pie chart?
A circular graph showing how a total amount is divided into parts. The size of each slice indicates a proportion of the whole.

  • Compare parts of a whole
  • Percentages must add up to 100%
  • Don’t use 3D or distort slices
  • Limit the number of slices
  • Storytelling shouldn’t depend on comparing similarly sized slices

Further reading

Related Discussions

Have questions about this video? Start a discussion with the community and Treehouse staff.

Sign up

    Related Discussions

    Have questions about this video? Start a discussion with the community and Treehouse staff.

    Sign up

    A pie chart shows how a total amount is divided into parts. 0:00
    The size of each slice indicates a proportion of the whole. 0:05
    You can imagine this as a literal pie. 0:09
    If I cut a pie into six equal slices, and eat one of them, 0:12
    we're left with a visual representation of how much of the pie has been eaten. 0:15
    That's one-sixth of the total pie, and the five-sixth of the pie that remains. 0:20
    Pie charts have a bit of a bad reputation amongst those who practice data 0:27
    visualization. 0:31
    One problem is, it's easy to distort the story told by the data. 0:33
    In a presentation at the 2008 Macworld Conference, Steve Jobs presented a chart 0:38
    boasting of Apple's 19.5% smartphone market share in the United States. 0:44
    Unfortunately, by placing Apple's share closer to the viewer, and 0:51
    applying a 3D effect, Apple managed to make their share look larger than 0:55
    the 21.2% slice attributed to other companies outside the top five. 1:00
    That doesn't mean pie charts can't visualize data effectively. 1:07
    I'm looking at a 2018 survey by the organization WebAIM or 1:12
    Web Accessibility In Mind asking questions about the daily practice of designers and 1:16
    developers with a focus on making accessible web products. 1:22
    Some of the pie charts here are pretty striking. 1:27
    As an educator who teaches web accessibility courses, 1:30
    I was disheartened to see that almost 93% of survey respondents didn't 1:34
    learn anything substantial about accessibility in school. 1:39
    The charts are additionally explained underneath using a table, 1:44
    which might benefit users who have trouble distinguishing 1:48
    the colors of the pie chart. 1:51
    We'll talk more about using color in a future video. 1:54
    What makes the pie charts found here more effective than many 1:58
    others found on the web? 2:01
    An article linked in the teacher's notes called, an updated post on pies, 2:04
    offers a set of solid guidelines. 2:09
    We've already learned to be cautious about 3D effects which add visual clutter and 2:11
    make the chart difficult to understand. 2:16
    In addition, since pie charts show each group's contribution to a whole, 2:19
    it's critical that your numbers add up to 100%. 2:24
    Here's a chart I found online visualizing the number of championships 2:28
    won by different NBA teams, but by eliminating championships won by any 2:32
    team other than the Celtics, Lakers, Bulls, or Spurs, 2:37
    it makes the Celtics' dominance look greater than it actually is. 2:41
    When designing pie charts don't have too many slices. 2:47
    I've made a quick rebuild of the NBA Championship winners in Google Sheets. 2:51
    And you'll see that trying to visualize every championship ever won in a pie chart 2:56
    gets awfully noisy. 3:01
    Grouping every team with fewer than five championships into a category called 3:03
    other makes the chart easier to read while ensuring the numbers still add up to 100%. 3:09
    Finally, since angular pie slices are difficult to compare to each other, 3:15
    make sure the story you're telling doesn't depend on a visual 3:20
    comparison of pie slices. 3:23
    Looking back at Apple's 2008 chart on smartphone market share, 3:26
    while the most obvious issue is the distortion of the chart, I'd argue Apple 3:30
    could have told a more meaningful story with these numbers using a bar chart. 3:35
    So let's summarize. 3:41
    Pie charts can be an appropriate visualization choice, but 3:43
    only when you're comparing parts of a whole and those parts add up to 100%. 3:47
    Don't use 3D or distort your pie slices. 3:52
    Keep the number of slices limited and 3:56
    make sure your story doesn't depend on comparing similarly sized slices. 3:59
    So that covers bar charts, histograms, and pie charts. 4:05
    In the next stage, we'll take a look at line charts, area charts, and 4:09
    scatter plots. Stick around. 4:13

    You need to sign up for Treehouse in order to download course files.

    Sign up

      You need to sign up for Treehouse in order to set up Workspace

      Sign up