The world looks almost eerie when you look at it as a graph of Facebook relationships. The map is the brainchild of Facebook intern Paul Butler, who wanted to measure the geography of friendships and see how political and geographical boundaries affect friendships.
The data was already available, and Butler used a sample of 10 million friend pairs, correlating them to their current cities and mapping them. Showing the direct mapping was only the start though, and Butler then had to find a way to organise the data so it would measure out something recognisable, a challenge he addresses in a note he wrote on Facebook:
“I began exploring it in R, an open-source statistics environment. As a sanity check, I plotted points at some of the latitude and longitude coordinates. To my relief, what I saw was roughly an outline of the world. Next I erased the dots and plotted lines between the points. After a few minutes of rendering, a big white blob appeared in the center of the map. Some of the outer edges of the blob vaguely resembled the continents, but it was clear that I had too much data to get interesting results just by drawing lines. I thought that making the lines semi-transparent would do the trick, but I quickly realized that my graphing environment couldn’t handle enough shades of color for it to work the way I wanted.
Instead I found a way 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.”
The end result of Butler’s fiddling with the data is the slightly unearthly map of, well, the Earth. The map isn’t really unexpected – the US looks like a giant fizzing firework, while Western Europe and England are brightly lit up. India looks like a bright constellation, while most of Africa is still the Dark Continent.
China and Russia don’t seem to show up on the map though, although a lot of intersections take place within their territory, and Canada also seems to have a scattered presence, lacking the densely packed luminosity of its neighbour.
Source: Facebook [http://www.facebook.com/notes/facebook-engineering/visualizing-friendships/469716398919]