These are both fantastic. It has been 25 years since I had a serious math class (no Stats either - Set Theory, Category Theory), so this has taken me a few afternoons to wrap my head around.
Spline? Cubic? Bicubic? RBF? Shephard? And that's just interpolation.
Its weird that the Commons Math doesn't seem to have anything that is Linear or Bilinear. Everything is Bicubic.
Fastmath is a nice wrapper over all of these things. The bilinear function wraps the BilinearInterpolation class from Smile. Incanter has an interpolate-grid function as well, but Incanter hasn't been touched for a while and Fastmath has a lot of updates.
More interesting is that I am not using this for image processing. It is for Computer Assisted Testing. If you get an question right or wrong, you get a different next question. But the next isn't just based off right/wrong, it has a lot of other input. They are essentially doing Nearest Neighbor but want it to be smoother. I wonder if doing Bicubic would give the same results as Bilinear.
Thanks so much for the pointers, I really appreciate it.
Charlie