Visualizing Friendships, one level down

Fascinating and beautiful post from Paul Butler on the Facebook blog (see above) - here is how it was done, using teh open source stats package R:

....to simulate the effect I wanted. I defined weights for each pair of cities as a function of the Euclidean distance between them and the number of friends between them. Then I plotted lines between the pairs by weight, so that pairs of cities with the most friendships between them were drawn on top of the others. I used a color ramp from black to blue to white, with each line's color depending on its weight. I also transformed some of the lines to wrap around the image, rather than spanning more than halfway around the world.

After a few minutes of rendering, the new plot appeared, and I was a bit taken aback by what I saw. The blob had turned into a surprisingly detailed map of the world. Not only were continents visible, certain international borders were apparent as well. What really struck me, though, was knowing that the lines didn't represent coasts or rivers or political borders, but real human relationships. Each line might represent a friendship made while travelling, a family member abroad, or an old college friend pulled away by the various forces of life.

Later I replaced the lines with great circle arcs, which are the shortest routes between two points on the Earth. Because the Earth is a sphere, these are often not straight lines on the projection.

Friendship is beautiful! I immediately was drawn to 3 points from my neck of the woods - the bright point just East of Cape Town and the 2 points east of Madagascar - which were these heights of Southern Hemisphere internet usage (see below)


The bright points in the middle of the Indian Ocean are of course Reunion and Mauritius, who would have thought that such small islands will be so busy! I was interested in the point of light in SA on the coast (turns out it's the George/Knysna/Mossel Bay area).

These are by and large all tourist beach holiday territories*, clearly not everyone can turn themselves away from the seduction of the Internet, even in paradise

The other thing that interested me were these points in the middle of the Sahel (look for th deep V links):


One wonders what those are.....

*Actually, George, Reunion town etc - they are also the local admin towns as well, even paradise needs an infrastructure.... note how George is only really linked to Cape Town and Port Elizabeth rather than up to Johannseburg. Hubs and Spokes and all that.