I want to use "QwtSpline" for Periodic Spline Interpolation in my application. My problems are:

1) I don't know the period after which the spline repeats.
2) I also assumed following periods but this doesn't worK:
i) Period = max. input time val. - Min. input time val.
ii) Period = 2 pi
iii) I also checked with 2000 input time values with the distance of 0.001. But I have seen the output not repeating but instead increasing
3) I also tried to understand the script, but I couldn't pick how can the period be determined

If any one could help me in this matter, I would be so thankful.

Regards,
Zahid Raza