To answer the question of using data not normally on the MATLAB path, I offer the following modification.
warning ('This was an entry to the MATLAB programming contest (http://www.mathworks.com/contest/datavis/home.html). Please load the contest data and unzip it to place contest_data.mat on your MATLAB path.')
I find this interesting. I like that you make an animation work and there is a certain excitement seeing things look to level off early, then thinking there is no hope for improvement, but watching the spiral relentlessly optimize the solution.