Rock Around The Clock

Thursday, August 14, 2008 by Jon Peltier
Peltier Technical Services, Inc., Copyright © 2025, All rights reserved.

My friend Chandoo proposed a chart to show website traffic vs. time of day in Plot your data around the clock [Excel charting idea]. He thought he’d use the analogy of a 12-hour analog chart, and put a bubble at each hour, where the size of the bubble is related to the pageviews during that hour. Well there’s 24 hours in a day and 12 hours in a clockface, so he had to make a pair of charts. Here’s the result:

[画像:Chandoo's Double Bubble Chart Around the Clock]

Well, this probably seemed like a good idea at the time, and I like the fact that Chandoo keeps trying new ideas and shares them with his readers. But this dual chart has some shortcomings. The chart reminds me of a pair of Elton John glasses with jewels all around the frame, or maybe if I draw a few lines, it looks like a bicycle. And Dubble Bubble is a brand of chewing gum, not an Excel chart type.

Issues with the chart

1. The data is a time series, but it’s presented nonlinearly in two separate sections, and the passage of time is only implied by the parallel to an analog clock.
2. The horizontal line made me wonder at first where the jump occurred between left and right charts. Finally I downloaded the data and saw that the jumps occurred at midnight and noon.
3. The bubbles do not show the relative pageviews clearly. I first looked at this goggle chart and thought it was telling be that there was a pair of peaks in the hourly pageviews, one around 9 am and another around 4 pm. This illusion was partly due to the bubbles and partly to the leap between sides of the chart.
4. The colors are deceiving. The brighter color (orange) made me think of daytime and the dark color (black) made me think of night. A better break for the colors you used would be 6AM to 6PM and 6PM to 6AM. But then my confusion over point 3 would be magnified.

Remediation

At first I thought a 24 hour circular clock might work better, since it removes the jump from left to right. It could be done as either a bubble chart or a radar chart. Then I realized that nobody would understand it. “Oh, you mean 6 am is to the right? I thought it was pointing down.”

The KISS principle requires us to “Keep It Simple”, which means a simple time series, using an Excel XY chart.

The data is a simple list of pageviews vs hour of day:

Chandoo's Double Bubble Chart Data

I modified it slightly, converting to a 24-hour time format, and plotting each point in the middle of the hour (i.e., the 5 am point is plotted at 5:30 am). I came up with the following chart, a simple time series.

Jon's Alternative Chart

I probably shouldn’t have pimped the chart this way, because most people won’t get it, but I colored the daytime points (6AM to 6PM) yellow and the nighttime points (6PM to 6AM) dark brown. People would more likely get it if I used smiley suns for daytime and a happy moon for nighttime, but I’d probably lose clients over that.

As I said, I appreciate Chandoo’s effort here. Innovation is partly about trying strange new things. However, this was a case where simpler is in fact better. As any innovator would tell you, most innovations end up on the cutting room floor.

Update

Jorge Camoes has chimed in with a radar chart solution in Charting around the clock.

Jorge Camoes' Curator's Egg Chart

I have the same issue with this radar chart as I had with Chandoo’s double-trouble bubble chart. I don’t know where the day and night series cross, unless I read the fine print and point with my fingers on the screen until I locate the 8AM-8PM crossover.

In Jorge’s spirit of consensus, I’ve created my own 12-hour circular graphic, which addresses my conceptual problems with the charts shown thus far. It’s actually a combination radar-XY chart, using the radar to reproduce Jorge’s nice Roman-numeral clock face, and the XY series uses Chandoo’s trig algorithms to locate the actual data.

Jon's Alternative Chart

I show how I made this chart in Radar-XY Combination Chart