Qwt spline fitter - it doesn't work as expected

[giaur]

Ok, parametric spline is quite good - it looks the same as on my screenshot. But there is still some effect which I neew to minimalize - I need only edges round, and minimal curve peeks. For cardinal spline, there is parametr called tangentStrength and I can play with it to get bes results.

I simply need the situation, when maximum/minimum data point is curve maximum/minimum (ideally) and cardinal spline in my screen looks better here