Re: fixed points piecewise-linear fitting

[Martin Helm]

Am 21.03.2012 00:25, schrieb Ben Abbott:
> Using methods "linear" or "spline" give the same result. However,
> using your approach "cubic"/"pchip" doesn't produce a minimum least
> squares solution. I've attached a test script (go_ppfit.m) and both
> ppfit.m (mine) and ppfit2.m (yours). I modified yours to support
> weighted least squares. Ben
Well that makes of course sense since f(a*x+b*y) = a*f(x)+b*f(y) is not
valid for the pchip interpolants (I naively did not think about that
case) while it is true for piecewise linear and spline interpolants.
Thanks for having a further look and adjusting. Your function is very
useful. Do you plan to add it to octave or octave forge?