Spline interpolation degree question

[sandon]

Hi,

I working on code that does image tracking with missing pixels, but I noticed that higher ordered spline interpolation is unstable. Found through trial and error that the best result is degree 3, picture related. I always thought that spline interpolation does not display behaviours shown in the picture because they are conducted piece by piece over the data set. Is there a numerical explanation for this behaviour?

P.S interpolation done in python with scipy library

 

[mfb]

If the distances between your data points differ by large factors I'm not surprised that high order splines do strange things. It is the same behavior you see outside the interpolation range (as extrapolation).