November 08
This year’s cartograms are in, for a nice compromise between an electoral map, which is distorted by things like a 3,589 square mile county with less than 700 inhabitants, and a big board, which suffers from looking like a really shitty math assignment.
That being said, I expect Clark’s Last Biscuit and Non-Prophet to geek out with me on his methodology:
The calculation of the cartograms involves allowing the population to diffuse in the two-dimensional space of the map, carrying the boundaries of the states or counties with it, until it reaches a uniform equilibrium. The diffusion equation is integrated in Fourier space, where it takes a particularly simple form: the initial density function is evaluated on a 4608×3072 lattice, transformed using a two-dimensional fast Fourier transform, convolved with a Gaussian kernel and then back-transformed to give the diffusion field at an arbitrary later time. I used closed (Neumann) boundary conditions at the edges of the map, meaning that the Fourier transform in this case is a discrete cosine transform.
The diffusion field is then used to calculate the diffusion velocity as a function of position and the velocity integrated over time to give the displacement of the map features. The integration is performed using a fourth-order Runge-Kutta integrator with an adaptive step size and local extrapolation.
Posted by: Andrew Hutchison in Election '08 | Permalink
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7 Responses to “Data porn”
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Schweet. I always think this stuff is pretty cool.
Am I supposed to say some nerd stuff now? How about: “Neumann? Real men use Dirichlet, pussy.”
You could say that, but I think it would be kind of abrupt.
Wow. I bow to your nerd comeback.
People might need some explanation of what just went down there.
If you wanna see a cartographic geek-fest, you should check out the book, Atlas of the Real World .
It’s amazing.
I guess we know where they found the Southland Tales image:
http://www.impawards.com/2007/posters/southland_tales_ver2.jpg
Now we just wait for the nuclear attack.
Er, try this one:
http://img.photobucket.com/albums/v41/CaptainAlfred/southland-tales.jpg