Episode 21: How to Gain Insights by Identifying Intervals in Your Line Chart - Featured Data Visualization by Ben Jones
Welcome to episode 21 of Data Viz Today. How can segmenting your line chart into intervals help you gain insights into your data? Host Alli Torban dives into specific ways you can visually break up your line chart into intervals as a way to quickly see your data from a different perspective. Example questions you could answer: Which marketing campaign had the greatest effect on sales? Does varying the basketball shot clock length change how many points are scored? Featured data visualization by Ben Jones perfectly models how this technique can visually communicate a relationship between two metrics.
Welcome! I'm Alli Torban.
00:25 - Today’s episode is about visually breaking up your line chart into intervals to help see how your metric’s variation coincides with something else, so that you can gain insights and possibly take action. What are some examples where this would be helpful and how can you create your own?
01:20 - Today’s featured data viz project is called “Monthly US Unemployment Rate by Presidential Term” by Ben Jones. Ben is a technical evangelism director for Tableau Software and teaches data visualization at the University of Washington.
01:55 - Ben created his viz because he noticed that Political leaders often claim credit or assign blame for economic indicators, such as the seasonally adjusted unemployment rate, but he wanted to understand how this particular indicator has changed over time in the United States, relative to the presidential administrations that have coincided with the periodic swings. His goal was to plot the unemployment rate over time, and see how the presidential terms coincided with rise and fall of the unemployment rate.
02:25 - Ben grabbed the unemployment rate from the Bureau of Labor and Statistics website. He added columns for president and party.
02:50 - He used Tableau, and visually showed us the presidential intervals by using color, vertical lines, and labels at the top.
04:30 - You can quickly look at this chart and visually comprehend how the presidential terms coincided with rise and fall of the unemployment rate, which was Ben’s goal.
05:15 - Lots of use cases for plotting metrics over time and identifying intervals of change in power or leadership, like Ben did, whether it’s the president, or the CEO of a company.
05:28 - You could also use it build a viz that will help you visually understand the impact of different marketing campaigns on a metric that’s important to you. Great way to visually assess periods of experimentation.
06:15 - Other examples could be plotting sales and visually identify intervals where there was a tariff in place or not.
06:26 - Or in sports, you can plot a particular metric and visually identify intervals where different rules were in place to see if that rule might have been affecting the game in some way.
06:40 - My inspired viz: Showing the average points per game in Men’s College Basketball in the ACC from 1977 to 2017 and identifying the intervals by what kind of shot clock was in place at that time.
07:25 - My goal was to plot the average points per game over time, and see how the change in the length of the shot clock coincided with the rise and fall of the scores. I used Tableau. See it here:
09:35 - Final takeaway is that you can visually break up your line chart into intervals to help see how your metric’s variation coincides with something else. Then when you add small things like coloring the line by which interval it’s in, adding vertical markers, labeling each interval at the top and in the same color, and even adding trend lines or average lines, and then you have a powerful tool to assess what’s going on.
10:15 - Listen for Ben’s 8 tips for data viz newbies!
11:15 - Follow Ben on Twitter! @dataremixed
11:42 - Get mapping right away with my free-mini course “Make Your First Custom Map in Under 30 Minutes”.