How about this one? (The green curve does not look like monotonic to me
though ... The blue curve is the reference you cited)
MESA/INTERP_1D
monotonicity preserving cubic interpolation
piecewise monotonic cubic interpolation
http://mesa.sourceforge.net/interp_1D.html
On Thu, Mar 1, 2012 at 1:30 PM, Christian Krueger <address@hidden
<mailto:address@hidden>> wrote:
>
> Hi... is there any possibility to get a strictly monotone
interpolation function?
>
> I have data which for sure have to be monotone, but the provided
interpolation methods (cspline, akima) do not preserve this condition
(linear interpolation is not smooth and polynomial of course useless
with 200+ datapoints).
>
> I wonder whether the method of Steffen (1990) is implemented
somewhere which seem to have some nice features (monotonicity, almost no
spurious oscillations)? Or might it be a useful extension for GSL?
> Found in this paper: A simple method for monotonic interpolation in
one dimension, Astron. Astrophys. 239, 443 (1990)
>
>
> Regards,
> Christian
>