data visualisation – Page 2

The Great British Baking

Recently the United Kingdom baked in a significant heatwave. With climate change being a real thing, an extreme heat event in the summer is not terribly surprising. Also not surprisingly, the BBC posted an article about the impact of climate change.

The article itself was not about the heatwave, but rather the increasing rate of sea level rise in response to climate change. But about halfway down the article the author included this graphic.

As graphics go, it is not particularly fancy—a dot plot with ten points labelled. But what this piece does well is using a dot plot instead of the more common bar chart. I most typically see two types of charts when plotting “hottest days” or something similar. The first is usually a simple timeline with a dot or tick indicating when the event occurred. Second, I will sometimes see a bar chart with the hottest days presented all as bars, usually not in the proper time sequence, i.e. clustered bar next to bar next to bar.

My issue with the the latter is always where is the designer placing the bottom of the bar? When we look at the best temperature graphics, we usually refer to box plots wherein the bar is aligned to the day and then top of the bar is the daily high and the bottom of the bar the daily low. It does not make sense to plot temperatures starting at, say 0º.

In this particular case, however, the dates would appear to overlap too closely to allow a proper box plot. Though I suspect—and would be curious to see—if the daily minimum temperatures on each of those ten hottest days have also increased in temperature.

As to the timeline option, this does a better job of showing not just the increasing frequency of the hottest days, but also the rising maximum value. In the early 20th century the hottest day was 36.7ºC, and you can see a definite trend towards the hottest days nearing and finally surpassing 40ºC.

I do wonder if a benchmark line could have been added to the chart, e.g. the summertime average daily high or something similar. Or perhaps a line showing each day’s temperature faintly in the background.

Finally, I want to point out the labelling. Here the designers do a nice job of adding a white stroke or outline to the outside of the text labels. This allows the text to sit atop the y-axis lines and not have the lines interfere with the text’s legibility. That’s always a nice feature to see.

Credit for the piece goes to the BBC graphics department.

A New Downtown Arena for Philadelphia?

I woke up this morning and the breaking news was that the local basketball team, the 76ers, proposed a new downtown arena just four blocks from my office. The article included a graphic showing the precise location of the site.

I have no doubt whatsoever this won’t impact my commutes.

For our purposes this is just a little locator map in a larger article. But I wanted to draw attention to two things in an otherwise nice map. First, if you look carefully on the left you can see the label for the Broad Street Line placed over the actual railway line, which is what makes it so difficult to read. I probably would have shifted the label to the left to increase its legibility.

Second, and this is a common for maps of Philadelphia, is the actual north-south route of said Broad Street Line, one of the three subway lines running in the city. (You all know of the Broad Street and Market–Frankford Elevated, but don’t forget the PATCO.) If you look closely enough it appears to run directly underneath Broad Street in a straight line. But where it passes beneath City Hall you will see the little white dot locating the station is placed to the left of the railway line.

Why is that?

Well when it was built, Philadelphia’s City Hall was the tallest habitable building in the world. Whilst clearly supplanted in that record, the building remains the largest free-standing masonry building in the world. But that means it has deep and enormous foundations. Foundations that could not be disturbed when the city was running a subway line directly beneath Broad Street.

Consequently, the Broad Street Line is not actually straight—ride it heading south into City Hall Station and you’ll notice the sharp turn both in its bend and the loud screeching of metal. The line bends around parts of the building’s foundations, sharply on the north side and more gently on the south side. So the actual station is still beneath City Hall, but offset to the west.

But most of the time it’s easier just to depict the route as a straight line running directly beneath City Hall.

Credit for the piece goes to John Duchneskie.

Small Dog Days of Summer

For my readers in the northern hemisphere, which is the vast majority of you, we are in the middle of meteorological summer, the dog days. And whilst my UK and Europe readers continue to bake under temperatures greater than 40ºC (104ºF), the northeast United States and Philadelphia in particular is looking at a heatwave starting today that’s forecast to peak at a temperature of 38ºC (100ºF) this weekend and a heat index reaching 41ºC (106ºF) tomorrow.

Not cool.

Yesterday we examined a completely different topic, property tax increases in Philadelphia, but we contrasted that work with a heat index map from the New York Times. With the heatwave beginning this afternoon, however, it seemed apropos to revisit that contrasting article.

It begins with the map that we looked at yesterday. Of course yesterday was Tuesday. Today is Wednesday, and so you can already compare these two maps to see how and where the heat has shifted. Spoiler: the Southeast and Midwest.

It does so with a nice simple three-colour unidirectional spectrum from a light yellow to a burnt orange. And you can see the orange spreading up from the Gulf Coast and along the southeastern Atlantic Seaboard.

For those not familiar, the heat index is basically what the air “feels like” taking into consideration the actual temperature and the relative humidity in the air. Humans cool themselves via perspiration and when the air is excessively humid our ability to perspire decreases and thus the body begins to run hotter. Warmer temperatures allow the atmosphere to increase the amount of moisture it can contain and you can see all that Gulf and subtropical moisture carrying itself into the hot air moving up from the south.

Very not cool.

The piece also offers a look at the forecast for the heat index, showing the next six days. These small multiples allow the reader to see the geographic progression of the heat. Whereas today will be particularly for parts of the Midwest in southern Illinois and Indiana, tomorrow will see the worst for the Eastern Seaboard. Luckily the heat index retreats a bit, though as I noted above, the temperatures will continue to rise until Sunday, meaning higher temperatures, but lower relative humidity. For Philadelphia in particular we talking about 50% relative humidity tomorrow and only 35% on Sunday. That makes a big difference.

Overall this is a great piece despite the content.

Personally, I just can’t wait until summer.

Credit for the piece goes to Matthew Bloch, Lazaro Gamio, Zach Levitt, Eleanor Lutz, and John-Michael Murphy.

Legendary Adjustments

The other day I was reading an article about the coming property tax rises in Philadelphia. After three years—has anything happened in those three years?—the city has reassessed properties and rates are scheduled to go up. In some neighbourhoods by significant amounts. I went down the related story link rabbit hole and wound up on a Philadelphia Inquirer article I had missed from early May that included a map of just where those increases were largest. The map itself was nothing crazy.

We have a choropleth with city zip codes coloured by the percentage increase. I was thrown for a bit of a loop as I immediately perceived the red representing lower values and green higher values, the standard green to red palette. But given that higher values are “bad”, I can live red representing bad and sitting at the top of the spectrum.

I filed it away to review later, but when I returned I visited on my mobile phone. And what I saw broadly looked the same, but there was a disconcerting difference. Take a look at the legend.

You can see that instead of running vertically like it did on the desktop, now the legend runs horizontally across the bottom. In and of itself, that’s not the issue. Though I do wonder if this particular legend could have still worked in roughly the same spot/alignment given the geographic shape of Philadelphia along the Delaware River.

Rather look at the order. We go from the higher, positive values on the left to the negative, lower values on the right. When you read the legend, this creates some odd jumps. For example, we move from “+32% to +49%” then to “+15% to +31%”. We would normally say something to the point of the increase bins moving from “+15% to +31%” then to “+32% to +49%”. In other words, the legend itself is a continuum.

The fix for this would be to simply flip the running order of the legend. Put the lower values on the left and then step up to the right. For a quick comparison, I visited the New York Times website and pulled up the first graphic I could find that looked like a choropleth. Here we have a map of the dangerous temperatures across the United States.

Note how here the New York Times also runs their legend horizontally below the graphic. But instead of running high-to-low like in the Inquirer, the Times runs low-to-high, making for a more natural and intuitive legend.

This kind of simple ordering change would make the Inquirer’s map that much better.

Credit for the Inquirer piece goes to Kasturi Pananjady and John Duchneskie.

Credit for the Times piece goes to Matthew Bloch, Lazaro Gamio, Zach Levitt, Eleanor Lutz, and John-Michael Murphy.

Warming Towards Women Leaders

We are going to start this week off with a nice small multiple graphic that explores the reducing resistance to women in positions of leadership in Arab countries. The graphic comes from a BBC article published last week.

These kinds of graphics allow a reader to quickly compare the trajectory of a thing between a start and an endpoint. The drawback is it can obscure any curious or interesting trends in the midpoints. For example, with Libya, is its flat trajectory always been flat? You could imagine a steep fall off but then rapid climb back up. That would be a story worth telling, but a story obscured by this type of graphic.

I do think the graphic could use a few tweaks to help improve the data clarity. The biggest change? I would work to improve the vertical scale, i.e. stretch each chart taller. Since we care about the drop in opposition to women leaders, let’s emphasise that part of the graphic. There could be space constraints for the graphic, but that said, it looks like some of the spacing between chart header and chart could be reduced. And I think for most of the charts except for the first, the year range could be added as a data definition to the graphic and removed from each chart. Similar to how every row only once uses the vertical axis labels.

Another way this could be done is by reducing the horizontal width of each chart in an attempt to squeeze the nine from three rows down to two. That would mean two additional chart positions per row. Tight fit? Probably, but there is also some extraneous space to the right and left of each chart and a large gap between the charts themselves. This all appears to be due to those aforementioned x-axis labels. An additional benefit to reducing the horizontal dimensions of each chart is it increases the vertical depth of the chart as each line’s slope, its rise over run, sees its horizontal distance shrink.

Overall this is a really smart graphic that works well, but with a few extra tweaks could take it to the next level.

Credit for the piece goes to the BBC graphics department.

It’s a Little Steamy Out There

And by out there I mean 1150 light years away. One of the five amazing images out of the first day’s announcement by the James Webb Space Telescope (JWST) team was not a sexy photo of a nebula or a look back 13.5 billion years in time. Instead it was a plot of the amount of infrared light was blocked as exoplanet WASP-96b, a hot Jupiter, transited in front of its sun. A hot Jupiter is a gas giant roughly the size of Jupiter that orbits its sun so closely—often closer than Mercury does our Sun—its year takes mere days. WASP-96b is about half the mass of Jupiter and a year takes a little over three Earth days. Hot indeed.

The JWST means not just to take those images we saw, but to also capture data about the light passing through planetary atmospheres, just like WASP-96b. And showing the world Tuesday just how that works was a brilliant idea. What they shared was this graphic.

The original post explains the science behind it, but in short we see telltale signs of water vapor in the atmosphere. Remember that the planet is far too hit for liquid water to exist. But because the peaks and troughs were not as pronounced as expected, scientists can conclude that there are clouds and haze in the atmosphere. It did not detect any significant signs of oxygen, carbon dioxide, or methane, all of which would be noticeable if present as we expect in future exoplanets to be studied.

But later that day, the BBC published an article summarising the releases, but included a different version of the above graphic. Though the other four photos were unchanged. The BBC presented us with this.

The most notable difference is the background. What was a giant illustration of a planet and then a semi-transparent chart background atop that on which the graphic sat is here replaced by a simple white background. Off the bat this chart is easier to read.

But then here we also lose some data clarity. Note on the original how we have axis markers for the wavelengths of light and the parts per million of light blocked. All are absent here. Instead the BBC opted to only put “Shorter” and “Longer” on the wavelength axis. I would submit that there was no real need to remove those labels, but that they could have been added to with these new ones. The new labels certainly explain the numbers to an audience that may not be as scientifically literate as perhaps the JWST’s audience was or was thought to be. There is certainly a value to simplifying and distilling things to a level at which your audience can understand. But there’s also a value in presenting more complex data, issues, and ideas in an attempt to educate and elevate your audience. In other words, instead of always trying to play to the lowest common denominator, it sometimes is worth it to lose a few in the audience if you ultimately increase the level of said denominator overall.

The other notable difference is that the data is presented without what I assume to be plots of the range of observations with their respective medians. You can see this in the original by how every wavelength has a line and a dot sitting in the middle of that line. In other words, over the 6+ hours the planet was observed, at each wavelength a certain amount of light was blocked. The average middle point over that whole time period is the dot. Then a line of best fit “connects” the dots to show the composition of the light streaming though that steamy atmosphere.

Again, I can understand the desire to remove the ranges and keep the median, but I also think that there is little harm in showing both. Though, the first graphic could like have used an explanation of what was shown, as I’m only assuming what we have and I could be way off. You can show more things and raise the level of the denominator, but you can only do so if you explain what your audience is looking at.

Overall both graphics are nice and capture not just the particular makeup of this one exoplanet’s atmosphere, but more broadly the potential power of the JWST and its impact on astronomy.

Credit for the original goes to the NASA, ESA, CSA, and STScI graphics teams.

Credit for the BBC version goes to the BBC graphics department.

Those Quirky Quarks

Last week scientists working at the Large Hadron Collider in Switzerland announced the discovery of new sub-atomic particles: a pentaquark and tetraquarks. This BBC article does a really good job of explaining the role of quarks in the composition of our universe, so I encourage you to read the article.

But they also included a graphic to show how quarks relate to atoms. It’s a simple illustration, but it does a great job.

Sometimes great and informative graphics can be simple. They needn’t be flashy or over-designed. I could quibble about the depiction of the electron cloud around the nucleus, but it’s not terrible.

Credit for the piece goes to the BBC graphics department.

Choo Choo

I took two weeks off as work was pretty crazy, but we’re back to covering data visualisation and design with a graphic about trains. And anybody who knows me knows how I love trains. One of the early acts of the Biden administration was funding a proper expansion of rail service in the United States.

Last week the Washington Post published an article that explored some of the difficulties Amtrak, the national rail company, faces in that expansion. Most of it has to deal with the fact that outside the Northeast Amtrak largely uses rail lines owned by freight companies.

The article uses a map to show Amtrak routes and, in particular, where Amtrak wants to increase service or create new service.

As far as the map goes, it does a nice job needing not to reinvent the wheel. When an existing route will have expanded service, e.g. the Northeast Corridor, the blue line sits next to the dotted white line. What remains a bit unclear to me is the use of black text for Chicago, Atlanta, Dallas, and Los Angeles. The bold type for New Orleans and Mobile makes sense because of the story’s focus on that particular route. Chicago is mentioned once, but Dallas is not. So that is unclear.

But what really stood out to me was what happened when I re-read the story on my mobile. The graphic split from a full map to three narrow graphics, each featuring 1/3 of the United States. The designers moved the text labels so that they are fully visible in each graphic.

Overall, the piece does a great job at showing the map, but in particular it shines when it swaps out the large map for the smaller graphics on small screens. And the attention to detail in moving the text labels makes it all the better.

Credit for the piece goes to Luz Lazo.

Turn Down the Heat

First, as we all should know, climate change is real. Now that does not mean that the temperature will always be warmer, it just means more extreme. So in winter we could have more severe cold temperatures and in hurricane season more powerful storms. But it does mean that in the summer we could have more frequent and hotter heat waves.

Enter the United States, or more specifically the North American continent. In this article from the BBC we see photographs of the way the current heatwave is playing out across the continent. But it opens up with a nice map. Well, nice as in nicely done, not as in this is actually nice weather.

The only complaint most of my American readers might have is that the numbers make no sense. That’s because it’s all in Celsius. Unfortunately for Americans most of the rest of the world uses Celsius and not Fahrenheit. Suffice it to say you don’t want to be in the dark reds. 44C equals 111F. 10C, the greenish-yellow side of the spectrum, is a quite pleasant 50F.

And that can relate to a small housekeeping note. I’m back after a long weekend up in the Berkshires. I took a short holiday to go visit the area near that north–south band of yellow over the eastern portion of the United States. It was very cool and windy and overall a welcome respite from the heat that will be building back in here across the eastern United States later this week.

At least yesterday was the summer solstice. The days start getting shorter. And in about five weeks or so we will reach the daily average peak temperature here in Philadelphia. At that point the temperatures begin cooling towards their eventual mid-January nadir.

I can’t wait.

Credit for the piece goes to the BBC graphics department.

New Mexico Burns

Editor’s note: I was having some technical issues last week. This was supposed to post last week.

Editor’s note two: This was supposed to go up on Monday. Still didn’t. Third time’s the charm?

Yesterday I wrote about a piece from the New York Times that arrived on my doorstep Saturday morning. Well a few mornings earlier I opened the door and found this front page: a map of the western United States highlighting the state of New Mexico.

That doesn’t exactly look like a climate I’d enjoy.

Unlike the graphic we looked at yesterday, this graphic stretched down the page and below the fold, not by much, but still notably. The maps are good and the green–red spectrum passes the colour blind test. How the designer chose to highlight New Mexico is subtle, but well done. As the temperature and precipitation push towards the extreme, the colours intensify and call attention to those areas.

Also unlike the graphic we looked at yesterday, this piece contained some additional graphics on the inside pages.

Definitely not a place where I want to be.

These are also nicely done. Starting with the line chart at the bottom of the page, we can contrast this to some of the charts we looked at yesterday.

Here the designer used axis lines and scales to clearly indicate the scale of New Mexico’s wildfire problem. Not only can you see that the number of fires detected has spiked far above than the number in the previous years back to 2003. And not only is the number greater, the speed at which they’ve occurred is noticeably faster than most years. The designer also chose to highlight the year in question and then add secondary importance to two other bad years, 2011 and 2012.

The other graphics are also maps like on the front page. The first was a locator map that pointed out where the fires in question occurred. Including one isn’t much of a surprise, but what this does really nicely is show the scale of these fires. They are not an insignificant amount of area in the state.

Pointing out where I really don’t want to be in New Mexico.

Finally we have the main graphic of the piece, which is a map of the spread of the Calf Canyon and Hermits Peak fire, which was two separate fires until they merged into one. The article does a good job explaining how part of the fire was actually intentionally set as part of a controlled burn. It just became a bit uncontrolled shortly thereafter.

This reminded me of a piece I wrote about last autumn when the volcano erupted on La Palma. In that I looked at an article from the BBC covering the spread of the lava as it headed towards the coast. In that case darker colours indicated the earlier time periods. Here the Times reversed that and used the darker reds to indicate more recent fire activity.

Overall the article does a really nice job showing just what kind of problems New Mexico faces not just now from today’s environmental conditions, but also in the future from the effects of climate change.

Credit for the piece goes to Guilbert Gates, Nadja Popovich, and Tim Wallace.