On Thu, Jan 24, 2013 at 12:34:31AM +0100, Andreas Mueller wrote:
> Sorry, custom metrics for K means are not possible at the moment.

Yes, there is a massive difference in amount of work and performance when
you try to replace the Euclidean distance. Amongst other problems, the
mean is no longer the sum divided by the number of points, but the
Frechet mean, which requires solving an optimization problem.

Ariel, quite often, I find that use of distances adapted to the unit
sphere for clustering is over sold. If you have enough clusters, they do
not extend much on the sphere, and thus the sphere is locally equivalent
to a plane, and you can use standard Euclidean-based clustering
algorithms. If not, you have to pay the price, and it will be expansive.

G

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