I just found a well kept secret: "Periodic Splines in scipy", that I have to advertise. http://stackoverflow.com/questions/13490533/interpolating-data-in-python-wit... my quick plot based on their example: https://picasaweb.google.com/lh/photo/0YnsV6Ad6MlixKNfYW-g0dMTjNZETYmyPJy0li... Next time I need seasonal splines, I go for scipy. periodic at 3 decimals:

...

...

points[0], points[-1] (14.875105965386629, 14.874590980930265)

Josef Look, a new toy for my tool box.