Data Visualization

General best practices

Throughout the data visualization process, keep in mind some general best practices.

What is your purpose--exploratory or explanatory?
A main point to consider is if your visualization is meant to be exploratory (something you are doing to get more familiar with your data) or explanatory (you know your result and want to communicate it to your audience). See here for additional examples of explanatory vs exploratory visuals.

For an example that applies her five best practices in a viz showing philanthropic impact, with before and after views, see Cole Nussbaumer Knaflic's blog post Lessons from GMN.

Preattentive attributes

Our brains use certain characteristics like color, shape, and position to understand the relationship between different graphic elements.  Do these points represent the same type of data? How are they different from each other? Make the most of these visual characteristics, but don’t overdo it or the user can be overwhelmed. Emphasize attributes in this order of importance:​​

 

  1. Position
  2. Color
  3. Size
  4. Shape

Preattentive Attributes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Overcome memory limits

Even the best visualizations can tax the user’s memory limits. There are a number of ways to prevent this:

 

  • Use familiar chart types 
    There's a reason pollsters and newspapers use bar charts a lot--readers don't have to invest time figuring out the results.
  • Don't make people remember views
    It makes decoding your viz harder and more time-consuming than it needs to be. 
  • Avoid large legends
    Making legends part of your title, or labeling graphic elements directly, may reduce the work needed on the part of the user. 
  • Use intuitive colors and shapes
    As Yost points out, the traffic light metaphor of red means stop and green means go does not need to be explained, nor does red versus blue in U.S. political polls. 

Memory Limits

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A related best practice, introduced by Edward Tufte, is to maximize the Data-Ink Ratio. The Visual Display of Quantitative InformationIn his 1983 book, The Visual Display of Quantitative Information, he suggested:

 

A large share of ink on a graphic should present data-information, the ink changing as the data change. Data-ink is the non-erasable core of a graphic, the non-redundant ink arranged in response to variation in the numbers represented.

 

Use the 5 second test

If users can’t figure out your viz within 5 seconds, rethink your approach. Here are some ways to pass the test, using Andy Cotgreave's viz on road fatalities as a model:

  • Position the most important view goes on top or top-left
  • Position legends near their views
  • Avoid using multiple color schemes on a single dashboard
  • Use 5 or fewer views in dashboards
  • Provide interactivity
  • Carefully word Titles, Axes, and Units
  • Highlight key facts and figures

Fewer people are dying on US roads, but seasonal trends persist

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ten simple rules for better figures
PLOS Computational Biology
Nicolas Rougier, Michael Droettboom, Philip Bourne, PLoS Computational Biology, 2014

This article offers brief "do" and "do not" guidelines for making effective scientific figures and shows why they're useful. The first rule--Know your audience.


DataViz cheatsheet

    by PolicyViz
This cheatsheet briefly summarizes standard considerations for data visualization. A nice reference guide to keep in mind for each data visualization project.

 

For further information, see these U-MN Libraries ebooks:

Storytelling with Data: A Data Visualization Guide for Business Professionals Storytelling with Data: A Data Visualization Guide for Business Professionals

      by Cole Nussbaumer Knaflic

 

 

Information Visualization: Perception for Design  Information Visualization: Perception for Design

       by Colin Ware

 

 

The Big Book of Dashboards: Visualizing Your Data Using Real-World Business Scenarios  The Big Book of Dashboards: Visualizing Your Data Using Real-World Business Scenarios

       by Steve Wexler, Jeffrey Shaffer, Andy Cotgreave

 

 

Fundamentals of Data Visualization  Fundamentals of Data Visualization

       by Claus Wilke

 

 

Data points: Visualization That Means Something  Data points: Visualization That Means Something

       by Nathan Yau

Choosing the right chart type

The first step in effective data visualization is making sure you're using the right chart/graph type for your specific data. Here are some good overviews of your choices and why certain ones make more sense in certain situations.

Consider your underlying question

Jami Oetting, Hubspot
This overview about choosing the best type of graph for data frames the issue in terms of underlying statistical question. For instance, are you comparing values? Showing composition? Looking for trends? Interested in distribution? What you're trying to understand from your data can and should inform the type of graph you use to visualize and communicate the results.

 

 

Selecting the right graph for your message

Stephen Few, Perceptual Edge

 

 

Choosing by data type

Data analyst Yan Holtz and designer Conor Healy KANTAR Information is Beautiful Awards 2018
This guide frames the decision of which chart type in terms of data type: numeric, categorical, mixed numeric and categorical, maps, network, or time series. Click through to read more about caveats associated with each type of chart.



Working with qualitative data

Jennifer Lyons and Stephanie Evergreen, author of Presenting Data Effectively
Working with qualitative / non-numeric data can pose a set of different issues. The Qualitative Chart Chooser frames chart choice by what "story" you want to tell with your data.

 

 

Chart type generalizations

Larry Silverstein, "From "huh?" to "a-ha": The science of data visualization," Tableau Conference 2017 (slide 52)

 

Time: on an x-axis
Location: on a map
Comparing values: bar chart
Exploring relationships: scatter plot
Relative proportions: treemap

 

To encode trends over time, use a line graph instead of a bar chart.

 

 

Rules for charts

Nathan Yau, Flowing Data
This post provides examples of good and bad charts, distilled into a handful of general rules for making charts. For instance, be mindful of the starting point of the y-axis on a chart so that data representation is truthful to the underlying data trends. For example, he shows the dangers of overusing pie charts:

 

Rules for charts

 

 

Choosing colors

Selecting colors for a figure may seem like an inconsequential task and people often stick with the default color scale of whatever visualization tool they're using. This may not be the best choice, as misuse of color in data presentation may confuse the viewer and lead to misinterpretation of results. It is important to think through your color choices in order to best present your data and make the main points of a graph or chart easy for viewers to correctly figure out.

 

Color blindness (a.k.a. colour vision deficiency, or CVD) "affects approximately 1 in 12 men (8%) and 1 in 200 women in the world." So attention to color is an accessibility issue as well. Color blindness by Elijah Meeks & Susie Lu takes user-specified color input and displays what various colored graph types would look like to people with types of colorblindness.

 

Limit your colors to ~8. Research has shown that “humans can only distinguish ~8 colors,” so too many colors can overwhelm the user.

Too Many Colors   

 Right Number of Colors

For another before-and-after example of this effect, look at the Limit Colors section of Tableau’s Visual Best Practices guide.

 

What to consider when choosing colors for data visualization

Lisa Charlotte Rost of Datawrapper
A quick overview of what to consider when choosing colors for different type of graphs. One important question is: what do you want the viewer to take away from the graph?


Generate color palettes

Learn UI Design
This interactive website helps users generate a usable color palette. Also check out the "single hue" and "divergent" choices. A similar website, Colorgorical, lets users specify hue, lightness, and other technical color characteristics when creating a color palette.


Additional websites and tools

Lisa Charlotte Rost of Datawrapper
This post includes lots of links to additional tools for using color effectively in visualization.

Sources

"About Us." Colour Blind Awareness. http://www.colourblindawareness.org/about-us/. Accessed August 14, 2020.

Cotgreave, Andy. "Fewer people are dying on US roads, but seasonal trends persist." Tableau Publichttps://public.tableau.com/en-us/gallery/seasonal-trends-us-car-accidents. Accessed August 14, 2020.

Knaflic, Cole Nussbaumer. "Exploratory vs Explanatory Analysis." Storytelling with Data
http://www.storytellingwithdata.com/blog/2014/04/exploratory-vs-explanatory-analysis. Accessed August 14, 2020.

Silverstein, Larry. "From "huh?" to "a-ha": The science of data visualization." Tableau Conference, 2017, https://tc18.tableau.com/sites/default/files/session/assets/18BI-030_ScienceOfDataVisualization.pdf. Accessed August 14, 2020.

Last Updated: Nov 18, 2022 3:15 PM