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June 22, 2017

Makeover Monday: Tiled Heatmap of U.S. Air Quality Levels

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Yesterday I was at Exasol HQ trying to help them with their hackathon. I wasn't able to access their data for the hackathon, so I decided to do some testing for them with this week's Makeover Monday data set.

I was very interested in looking at state-level air quality and built lots of heatmaps and originally built them in a single worksheet using table calcs to sort out which states go in which columns and rows.


This didn't work for me, though, because it only helped me see the states alphabetically. It's much more intuitive if they are displayed geographically. An idea popped into my head...

I wonder if I can combine a heatmap that looks at daily max reading by state across all years with a tile map.


I quickly went to Matt Chambers' great post for how build tile maps added the secondary data source, blended it by state and replaced my crazy table calcs with a simple tile map view. What a fun exercise! I learned a ton and feel like I created a much more intuitive view. Does anyone recall every seeing a tiled heat map? Have I come up with a new chart type???

Click on the image for the interactive version. Note that the viz might be slow to load as it's displaying about 460,000 marks.

June 19, 2017

Makeover Monday: Is America Improving Its Ozone Air Quality?

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Eva and I are hosting another BrightTalk webinar this Friday titled "Visualizing Smart Cities: How Data can help shape our communities". This is part of an Internet of Things week for BrightTalk so when deciding what data set to pick for this week, I got to thinking about air quality sensors. A quick google search turned up a treasure trove of data on the EPA website. Thanks for my friends over at Exasol, I was able to create a place for all of us to play with all 202 million hourly measurements. If you want to play with the live connection to all 202M records, you will need a login which you can create via this registration if you do not already have one.

The EPA website also contained some basic reporting, which is the focus for this week's makeover.


What works well?

  • Simple layout. It's easy to see you have days within months going left to right and years going down.
  • Colors match the official EPA colors for the AQI categories
  • Including the ranges we know what constitutes a good reading vs. a bad reading
  • The title tells me what I'm looking. Including the date range is a nice touch too.
  • Using a strip plot along with the colors helps reveal seasonal patterns
  • Including the source in the footer

What could be improved?

  • Make the colors color-blind friendly
  • It's difficult to see how a month has changed across the years.
  • I can't hover to see the values.
  • It says each “tile” represents one day of the year and is color-coded based on the AQI level for that day, but I think it's actually showing the max measurement for each day. It should be more clear what they are representing.
  • There's very little context. How does one county compare to others? How does one county compare to the national average? 

What were my goals?

  • Last year I challenged The Data Duo to visualise an almost identical data set. Pooja created a pretty amazing viz (of course), so I wanted to pick some parts off of it. Particularly, the State selectors on each site and the dot plot.
  • I wanted to understand how each month changed across the years, which is pretty much exactly what a cycle plot was created for. I used a trend line instead of an average though because that seemed to show the patterns better.
  • I wanted to add context for comparisons to the national average and to the state average (which appears when you click on a state).
  • I wanted to use color-blind friendly colors.
  • I wanted a small sparkline-type chart to show how things have changed since 1990.

With these goals in mind, here is my Makeover Monday week 25 submission. Click on the image for the interactive version.

October 5, 2009

Follow up: Evolution of the Ozone Hole

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You know, I really love it when people discuss issues and share solutions. Joe Mako and I had a great discussion on my last two posts regarding the most effective visual representation of the ozone hole over time. Joe create an OUTSTANDING representation of the data using floating bars.



Joe created this visual using Tableau. I had not seen anyone do this in Tableau before. I had thought about doing stacked bars and making the lower of the two bars white, but this is way better. Joe has also provided the Tableau Packaged Workbook. I have posted this on a Google Group that I just created.

Thanks Joe! Excellent work!

Size Evolution of the Ozone Hole

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Joe Mako left a comment on my previous post critiquing the use of bubbles to represent the size evolution of the ozone hole. I agree with what Joe said: "a bar or line would have been better." The only problem with using a line is that there is not a consistent time measure (1996 throws it off...yes I know, a minor issue).

So I recreated the data with two bar charts. (1) Representing the actual values and (2) the change from the previous measure. I like (1) better. How about you?

October 4, 2009

Quick, help save the bubbles

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Someone, please help explain this to me. There is no legend to reference the colors, the data, nothing.

Why 1996 instead of 1995? What do the numbers represent? What do the colors signify? Why is the last bubble green instead of hot pink?

If the dark grey in the middle four circles represents the ozone hole and the total size of the circle is earth (which I can only assume), then I think it's a poor representation of the problem. Is the ozone layer really that huge? No, it's not.

Please someone, save me! No wait, don't save me, save the bubbles!
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