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Data Visualization - A Brief Overview

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North Raleigh Rotarian Katie Turnbull gave a great presentation at our Friday morning extension meeting about data visualization. Katie is a consultant at research and advisory firm, Gartner, Inc.

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Data Visualization - A Brief Overview

  1. 1. Data Visualization A (Very) Brief Overview
  2. 2. What’s your graphic IQ? O http://www.perceptualedge.com/files/Grap hDesignIQ.html
  3. 3. What is data viz? O Data visualization helps us translate numbers into a picture that we can interpret more easily. O Two of the biggest reasons to use data visualization are to… O Make sense of data (i.e., help you see patterns) O Communicate data to others (i.e., executive presentations) O Good visualizations allow our eyes to do some of the heavy lifting in data processing
  4. 4. What is data viz? O The low profit in Q2 is more apparent in the graph than in the table. Profit ($M) Q 1 $4.18 Q 2 $3.24 Q 3 $4.12 Q 4 $3.91 $0 $1 $2 $3 $4 $5 Q1 Q2 Q3 Q4 Profit ($M)
  5. 5. Audience matters! O Visualizations can be useful, even if you’re the only one to see them. O For presentations, consider if everyone will have a printed copy, or if they need to be able to see fine details on a screen. Q1 Q2 Q3 Group 1 4.19 4.25 4.50 Group 2 4.00 4.32 4.31 Group 3 4.22 4.18 4.54 Group 4 4.35 4.41 4.62 Q1 Q2 Q3 Group 1 4.19 4.25 4.50 Group 2 4.00 4.32 4.31 Group 3 4.22 4.18 4.54 Group 4 4.35 4.41 4.62
  6. 6. Purpose matters! O Presentations are often expected to function as both the visual aid during the meeting, and a reference for those unable to attend. O Alternatives: O 2 documents with difference purposes O Use “speaker notes”
  7. 7. Content matters! O Different chart types have different strengths and weaknesses. O Of the two options below, which do you think is easier to interpret? Why? 0% 20% 40% 60% 80% White/Caucasian Hispanic Black/African American Asian Two or More Races Prefer not to answer % of Population% of Population White/Caucasian Hispanic Black/African American Asian Two or More Races Prefer not to answer
  8. 8. Types of Data: Comparisons O Column charts are likely the best option if you have few groups (< 8), but title length can be a problem O Bar charts work better if you have more groups or longer titles O Heat maps are good if you’re comparing more than one group on more than one metric
  9. 9. Types of Data: Comparisons, continued O Bullet graphs have become popular in dashboards, since they’re a compact option to show a value against a specific metric as well as a showing what’s considered good, fair, and bad. 4.18 3.24 4.12 3.91 Q1 Q2 Q3 Q4 Poor Fair Good 2016 2015
  10. 10. Types of Data: Composition 75% 67% 82% 73% 13% 11% 12% 18% 12% 22% Question 1 Question 2 Question 3 Question 4 Fav Neu Unf O Stacked bar or column charts are frequently used for survey results O Pie charts can be used, but be careful to avoid common issues with pies IC 71% Mgr 26% Sr Ldr 3% Manager Status
  11. 11. Types of Data: Trend O Line charts are commonly used to display long-term trend data. 55% 60% 65% 70% 75% 2014 2015 2016 2017 Group 1 Group 2 Group 3
  12. 12. Types of Data: Relationship O Scatterplots are the most common graphic to show relationship data, but bubble charts can be used if you need to look at a third variable O You can also use line charts to see relationships by comparing the shape of the graphs O Network graphs can be used to show relationships between individuals 60% 70% 80% 90% 60% 70% 80% 90% 2017 2016
  13. 13. Tips for Useful Charts & Graphs O Use the full axis, particularly on column and bar charts O Highlight the most important information O Consider if legends and labels detract from your point O This isn’t to say you shouldn’t label your data, but sometimes it’s redundant or could be placed in a better way O Consider the “data-to-ink” ratio O Pass the “squint” test O Think about sort order O Ask for a second opinion
  14. 14. Common Problems in Presentations O Too much information O Poor color choices O Variety for the sake of variety O Inconsistent axes from one slide to the next O Neglecting to label charts O Not following common conventions
  15. 15. Making Bad Charts Better
  16. 16. Pretty vs. Useful Example from: http://viz.wtf/post/147196565281/alphabet-on-the-x-axis-for-reals#notes O While this chart is pretty and at least labeled, it’s hard to read quickly. Using an alphabetic scale on the x-axis doesn’t do anything to enhance interpretation.
  17. 17. Pretty vs. Useful, continued O This bar chart is a better option for conveying the same data. Example from: http://viz.wtf/post/147196565281/alphabet-on-the-x-axis-for-reals#notes
  18. 18. Poor Axis Choice Example from: http://junkcharts.typepad.com/junk_charts/2016/06/what-doesnt-help-readers-on-the-chart-and-what-does-help-off-the-chart.html The graph below uses a line to show trend (a common convention), but the upside-down, truncated y-axis makes it hard to read. A bar chart version would be easier to follow, but you could just fix the y-axis.
  19. 19. Republicans are bad at graphs… O Media sources with a clear bias are notorious for using a truncated axis to their advantage. 6 7.066 0 2 4 6 8 As of 3/27 3/31 Goal Millions Obamacare Enrollment
  20. 20. … but so are Democrats O In addition to truncating the axis, this one also fails to show that the upward trend started before Obama took office. Example from: https://qz.com/580859/the-most-misleading-charts-of-2015-fixed/
  21. 21. Yet Another Poor Axis Choice Example from: https://qz.com/580859/the-most-misleading-charts-of-2015-fixed/ O This is one of those times that it doesn’t make sense to start the y-axis at 0.
  22. 22. Yet Another Poor Axis Choice, continued Example from: https://qz.com/580859/the-most-misleading-charts-of-2015-fixed/ O The trend is more apparent when we use a more realistic axis.
  23. 23. How Not to Make a Pie Chart O Pie charts should never be used to show values on a multiple-select item. Use a bar or column chart instead. Example from: http://viz.wtf/post/162169270900/what-is-the-recidivism-rate-for-pie-chart Overall 0% 20% 40% 60% 80% RecidivismRate Offense Type
  24. 24. How Not to Make a Pie Chart, continued O While this pie does add up to 100%, the design of the graphic makes it nearly impossible to read. Example from: http://viz.wtf/post/60203066686/the-spiral-staircase-courtesy-of-janwillemtulp 0% 10% 20% 30% 40% 50% 60% ContrarianThesis PersonalFailure SnappyRefrain Statementof UtterCertainty Spontaneous Moment OpeningJoke Sophisticated VisualAids
  25. 25. Telling Your Story O The headline to go with this chart was “Price has declined for all products on the market since the launch of Product C in 2010.” Example from: http://www.storytellingwithdata.com/blog/2014/05/the-story-you-want-to-telland-one-your
  26. 26. Telling Your Story, continued O Since we’re looking at trend data, a line chart would make it easier to see where the points are for each year/product. Example from: http://www.storytellingwithdata.com/blog/2014/05/the-story-you-want-to-telland-one-your
  27. 27. Telling Your Story, continued O Alternate headline: “As of 2014, retail prices have converged across products, with an average retail price of $223, ranging from a low of $180 (Product C) to a high of $260 (Product A). Example from: http://www.storytellingwithdata.com/blog/2014/05/the-story-you-want-to-telland-one-your
  28. 28. Use of Color & Number of Groups 1 1.5 2 2.5 3 3.5 4 4.5 5
  29. 29. Use of Color & Number of Groups, continued 1 1.5 2 2.5 3 3.5 4 4.5 5 1 1.5 2 2.5 3 3.5 4 4.5 5
  30. 30. Appendix
  31. 31. Chart Chooser Chart Chooser from: http://extremepresentation.typepad.com/blog/2006/09/choosing_a_good.html
  32. 32. Why Are Pie Charts Disliked? O In each of these charts, can you identify the largest slice? How does it compare to the second largest? Example from: http://prsync.com/oracle/pie-charts-just-dont-work-when-comparing-data---number--of-top--reasons-to-never-ever-use-a-pie-chart--23294/
  33. 33. Why Are Pie Charts Disliked? O Here’s the same data as column charts- it’s much easier to see differences between groups. Example from: http://prsync.com/oracle/pie-charts-just-dont-work-when-comparing-data---number--of-top--reasons-to-never-ever-use-a-pie-chart--23294/
  34. 34. If You Really Need to Use a Pie Chart… O There are some do’s and don’t’s that are specific to pies if you really feel you need to use them. O Arrange the slices in a way that makes sense. O Don’t use them for more than 2-3 categories. O Don’t use 3D. Ever. O Add numeric values as labels so that the end user doesn’t have to guess. It’s also usually helpful to put the category in the label instead of using a legend. O Don’t “explode” your pies. O Don’t use pies for questions that allow more than one response.
  35. 35. Excel Tricks O Trying to get Excel to do something it’s not really designed to do? Check the Peltier Tech site. O https://peltiertech.com/Excel/Charts/ChartI ndex.html
  36. 36. More on Color Choices O Semantically resonant colors O https://hbr.org/2014/04/the-right-colors- make-data-easier-to-read
  37. 37. More on Color Choices O If you know someone in the audience is color-blind or will be printing the presentation, there are specific palettes that are “friendly”. O http://www.vischeck.com has examples of what various images look like to individuals with color-blindness O http://colorbrewer2.org gives sample “friendly” palettes
  38. 38. Other Resources There are several great data viz practitioners with excellent books and websites. Some to look for: O Stephen Few O Edward Tufte O Nathan Yau O Albert Cairo O Cole Nussbaumer Knaflic O Junk Charts http://junkcharts.typepad.com/ O WTF Visualizations http://viz.wtf/

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