Fitting models

[Sebastian Roller]

Hello,
i'm Sebastian.
I'm using octave in order to fit many values.
The values come from an engine-model of my university (hcci-model).
The person before me, used MATLAB, and my work is now, to do the same with octave.
In MATLAB is used the fitting function "smoothing spline". But this function is not available
in octave.
So my question is, if anybody knows a simiular function in octave and how to use it???

values:

x-axes: crank angle
y-axes: temperature(K) / pressure(bar)


Thanks Sebastian