Monday, December 24, 2018

A jolly, holly network ... of Christmas carols

Today is Christmas Eve. What could be more befitting for our merry blog than to show a network of Christmas carols?

The perfect result would, of course, be a snowflake-like network. Ideally, approaching what is called a "stellar dendrite snowflake".

Stellar dendrites. (Images from a post
introducing a snowflake book:
The Snowflake.)

The data

I browsed the internet for lyrics of Christmas carols, and then scored their content in the form of a binary matrix.

The "taxon set" includes 45 traditional and (more) modern carols, some of them listed here, along with some others I remembered and sought out (eg. here). A comprehensive list of traditional carols can be found here, but using this would have made the matrix much too large for a post on Christmas Eve. (If you are reading this before Christmas, you might be spending too much time on science.) A rule of thumb is that a matrix should always have at least as many (completely defined) characters as taxa.

The 45 (hohoho!) "characters" include:
  • length (short = 0, long = 1), and tone (merry = 0, darkish = 1)
  • topics it is about / relates to / mentions — e.g. the birth scene, love, and yuletide (the latter included because as a naturalized Swede, I love the jultiden, fancy julkaffe, and much enjoyed most of my julbord);
  • major Christmas figures — Jesus, angels, drummers, elves, Jack Frost, the Grinch, milking maids, monsters, Santa Claus, shepherds, snowmen, the Wise Men from the Orient;
  • mentioned animals, such as reindeer, and plants, including the Christmas tree (traditionally a Tannenbaum – fir tree), and (very important for Anglosaxons who don't kiss each other whenever they meet, like we do in France) the mistletoe
  • last but not least, Christmas related objects — non-living things such as bells, Christmas food, harps, sleighs, snow, stars, and presents.

The network

The result is not a perfect stellar dendrite, but it is close enough.

A Neighbor-net of Christmas carols. Stippled terminal edges are reduced by factor 2.

It has quite a nice circular sorting of the carols, each related in some way to the ones next to it. The only oddly placed one is "Twelve Days of Christmas", which is a very peculiar one (and my English, favorite), along with the rather content-free "We wish You a Merry Christmas".

Finally, as a Christmas treat, the "great voices of the British public" singing (and reflecting on) my favorite carol: a Creature Comforts Christmas special.

A merry Christmas to everyone!

And please try out some networks during the coming year.

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