Paul I did some visualizations for some slices of time:

[vector plot](http://files.lossofgenerality.com/http:/daniel_debug.pdf)

[Stream plot ](http://files.lossofgenerality.com/daniel_debug_stream.pdf)

I don't seem to see any problem in the code. I added the lm linear regression and it is kinda deceptive to come up with a a regression line for this data.


Daniel asked me to take the derivatives on the non-normalized coordinates, I will hack that code tonight sometime.

Dara