April 2, 2015

When Is Easter Sunday?

Easter Sunday is the Sunday following the first full moon after March 21. A few years ago I published this histogram of Easter Sunday dates. A friend then asked whether it was possible to visualize Easter Sunday dates from one year to the next. I've finally gotten around to producing such a visualization.

The time-series chart below shows 1000 years of Easter Sunday dates. You can find an interactive version here (modern browser required). Use the mini-chart to focus the top chart on a specific range of years.

This chart allows us to see repeating patterns in the sequence of Easter Sunday dates. The patterns don't always repeat exactly but the human visual system is good at spotting similar patterns. For example, I was quickly able to match the sequence of Easter Sunday dates starting in 1943 and 2038 (April 25, 21, 17, 13, ...). The sequences are identical for almost 30 years. If you spot any others please let us know.

Implementing this Easter Sundays chart was really just an excuse for me to experiment with the NVD3 library, a collection of reusable charts built atop the excellent d3.js library. The beauty of NVD3 is that it allows you to create fairly complex, interactive charts with only a few lines of code. The code I used is available here.

Happy Easter!

February 15, 2015

Triple-J Hottest 100 Artists 1993 – 2014

Triple-J's Hottest 100 is an annual music poll conducted by the ABC's youth radio station JJJ. The poll counts votes for listeners' favourite songs of the previous year, and has been run (in its current form) each year since 1993 with more than two million votes cast in 2014's Hottest 100.

I was curious to know which artists feature most prominently in the Hottest 100. So, I scraped the poll results for each year from Wikipedia, and used KNIME to aggregate entries for each artist. I then ranked artists by number of entries, followed by median entry position. This allowed me to come up with the "Hottest 100 Artists for 1993 – 2014".

I created an interactive chart using d3.js to visualize the Hottest 100 Artists. An interactive version of the chart is available here (you'll need a modern browser) and a screenshot shown below.

Hottest 100 Artists for 1993 – 2014. Interactive version here.

The chart is a scatter plot with a circle glyph for each Hottest 100 track by a popular artist. The position of a glyph is determined by its artist and the year it polled. Its colour denotes the track's rank in the poll (red=1; yellow=50; white=100). You can mouse-over a track to see more information about it, or mouse-over an artist/year label to highlight tracks for that artist/year.

We can see that Powderfinger currently tops the poll with 22 entries (median position 21.5; 1996 – 2009) followed by Foo Fighters (17 entries; median 37; 1995 – 2015). Lana Del Ray takes out the 100th position with five entries (median 32; 2011 – 2013).

I'll update and improve the chart in future years. Meanwhile, if you've any corrections or constructive criticism then please leave a comment. The source-code and data are available here.