This week, we are taking a look at a lesser used visualization type called a stream graph. Stream graphs are similar to a stacked area chart, but they have values displaced around a central axis rather than stacking on top of an axis.
They have received criticism in the past for being difficult to read, often related to the number of categories being displayed or the goals of the author conflicting with those the reader. Many people have suggested that legibility of a stream graph improves when adding interactivity. Andy Kirk wrote a great article in 2010 after a stream graph was published in the New York Times (it’s missing a few images, but it’s still a good read). One study has shown that static stream graphs are more effective than static stacked area charts for value comparison tasks.
I created my stream graph below using a custom visual from AppSource, but you can create yours in Charticulator or Deneb if you’d prefer. Note: one downside of the stream graph custom visual is that it currently does not include the ability to turn off the rather large tooltips that do not provide analytical value. That may be a good reason to use an alternative, but I wanted to provide a low-effort way to make the graph for WoW purposes.
Today we are visualizing how much of the continental US has been affected by drought over the last 2.5 years.
- Retrieve the data from US Drought Monitor.
- Shape your data so there is one column containing the drought category (as opposed to 6).
- Sort the region values so they match the following order: 1) West 2) High Plains 3) Midwest 4) South 5) Southeast 6) Northeast.
- Add a description and sort order for each drought category as follows:
Drought Category ID Drought Category Drought Cat Order None None 0 D0 Abnormally dry 1 D1 Moderate drought 2 D2 Severe drought 3 D3 Extreme drought 4 D4 Exceptional drought 5
- Create a stream graph using your choice of custom visual.
- Share your workout on Twitter or LinkedIn and let us know what you think of stream graphs!
This week’s data comes from the National Drought Mitigation Center at the University of Nebraska-Lincoln. Their website allows the download of data in CSV, JSON, or XML. If you’d like an extra challenge, you could use their web services. REST API.
To retrieve the data from the website, pen a web browser and go to https://droughtmonitor.unl.edu/DmData/DataDownload/ComprehensiveStatistics.aspx.
Set these options and then download your file:
- Start date: 01/01/2020
- End date: 06/30/2022
- Spatial Scale: Climate Region
- Statistics Category: Total Area
- Statistics Type: Cumulative
- MapDate (integer date ID representing the start of the week
- None (first drought category)
- D0 (second drought category)
- D1 (third drought category)
- D2 (fourth drought category)
- D3 (fifth drought category)
- D4 (sixth drought category)
- Valid Start (start of week)
- Valid End (end of week)
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.