2022 Week 35 | Power BI: Make a Comet Chart


This week we are exploring another lesser used chart type: the comet chart. Comet charts show the evolution of one or two measures over time. They allow you to see change between two time periods across a category while emphasizing the direction of the change. You might use a comet chart instead of a dumbbell chart, slope chart, or a bar chart with a comparison marker. 

We are going to make a single-dimension comet chart. 


  • Create a comet chart using the Deneb custom visual that compares the percent of Americans living alone in 1980 with those living alone in 2018 sliced by age group. (Hint: a comet is made by using a trail mark in Vega-lite.) 
      •  Change the color of the comet so it is different for comets that show an increase versus a decrease. 
      • Create a tooltip report for use with the comet chart. It should show the percent of Americans living alone in 1980 and 2018 as well as the difference between the two numbers. Feel free to add any other data points you’d like.
  • Create another visual of your choice that shows the trend for each age group from 1900 to 2018.
  • Add some text commentary about the trends identified in the visuals you have made.


This week’s data comes from Our World In Data. To obtain the data: 

  1. Go to https://ourworldindata.org/grapher/percentage-of-americans-living-alone-by-age
  2. At the bottom of the chart, select Download. 
  3. In the Data section, select Full Data (CSV). 
This will download a single CSV file to your local machine, which you can then import into Power BI.


After you finish your workout, share on Twitter using the hashtags #WOW2022 and #PowerBI, and tag @JSBaucke@MMarie, @shan_gsd, @KerryKolosko, and @NerdyWithData. Also make sure to fill out the Submission Tracker so that we can count you as a participant this week in order to track our participation throughout the year. 


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