forum.alglib.net

Needing to apply two constraints to one endpoint of a polynomial fit.

#1: Specified Value (Option 0).
#2: Specified 1st Derivative (Option 1).

The polynomialfitwc() works with either constraint; however, the specified 1st derivative option is forcing a changed endpoint value.

Possibly could duplicate the endpoint in the data arrays and apply the 2nd constraint to the duplicated point? But that feels very wrong.

Please advise. Thanks!

Hi! It is ok to supply duplicate xc[] to polynomialfitwc() as long as they have different dc[]. Yes, it is wrong to duplicate data point, but with distinct dc[] you actually have two distinct points, even if xc[] are the same. The first one constrains function value, the second one constrains its derivative.