I was pleasantly surprised to see that you got the coefficients and algorithms from that article working. I'm surprised it was a flipping of the coefficients. When I re-implemented it in Octave a flipped coefficient matrix caused for more havoc than the correctly oriented one. The "correctly oriented" Octave one was producing the same results as the Apache Math implementation, the transpose far far worse. Plus there was a coefficient flip change in the previous release which addressed the accuracy issues. Either way it's clear that the new code is working based on the tight tolerances of the new test, which is great news.
On the question of naming, this doesn't look piecewise to me. Yes, there are splines for each region rather trying to create an interpolation function for the entire region (which of course doesn't work). However I look at mine as "piecewise" because I don't calculate two-dimensional coefficients but rather interpolate in one axis for several lines in the second axis and then interpolate those results a second time. Is there a common name for the algorithm you implemented, like in the Akima spline? I'm fine with the existing chosen name for those objects if there isn't a specific name. It seems appropriate and descriptive. For 3+ dimensional interpolation the good news is that the brute force method I used can be extended pretty easily to higher dimensions. It is how I was planning on implementing Tricubic when I got time to work on this again. It works n-dimensionally because you just repeat that curve fitting and sampling for as many dimensions as you like. Rather than coding up a Tricubic explicitly maybe we can just code up the n-dimensional method instead. The overhead of the generalization to more than three dimensions shouldn't be dramatic. I hope to have more time after the beginning of next month to look at this if you would like me to try to take a whack at it. Hank On Sun, Nov 23, 2014 at 2:29 PM, Gilles <gil...@harfang.homelinux.org> wrote: > Hi. > > Please have a look at > https://issues.apache.org/jira/browse/MATH-1166 > > > Regards, > Gilles > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org > For additional commands, e-mail: dev-h...@commons.apache.org > >
