Eshwar - I considered offering a 5th order or higher fit when I wrote the code. I did not do so however, for valid reasons, at least what I considered valid ones.
- I've only rarely ever needed more than 3rd order. In one such case we were modeling paper paths through a copier, and the path needed to be smoother than a cubic spline could offer.
- Higher orders than a cubic are a serious problem for many of the most useful constraints one may want to apply. Monotonicity for example, is done using a set of necessary constraints based on an inequality from a Fritsch and Carlson paper. Higher orders than cubic however will not allow such a nice solution, so we would have problems ensuring true monotonicity. The curvature constraints would also be more difficult to satisfy.
So in the end, I chose not to implement higher orders than cubic. Sorry.
Hello John,
Thanks for this great tool.
I do have a question, I am not sure if it has been already answered. I would like pre-define the knots to be the points where the derivative of the curve changes sign. Is there an option for that? I am using the piecewise linear SLM fit, I can send you an example of my data if needed.
Thanks,
Judith
Evidently str2num used to work on cell arrays? To get it to work I had to change line 2451 from
numlabels(ix) = str2num(axlabely{ix});
to
numlabels(ix) = str2double(axlabely{ix});
Otherwise, it does just what I need, thanks!
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