[SciPy-user] splrep/splev versus interp1d

Johann Rohwer jr@sun.ac...
Wed May 21 03:24:42 CDT 2008


Hi,

What is the difference (in terms of the underlying algorithms) between 
splines generated by sp.interpolate.interp1d and sp.interpolate.splrep/splev?

As an example, when I do a simple spline interpolation of a sparsely sampled 
sin function, the two methods give me close but not identical results 
(especially close to the bounds of the x data the interpolated values differ).

Code:
import scipy as sp
sp.pkgload('interpolate')
x=sp.linspace(0,10,11)
y=sp.sin(x)
x2=sp.linspace(0,10,201)
tck=sp.interpolate.splrep(x,y,k=3)
y2=sp.interpolate.splev(x2,tck)
f=sp.interpolate.interp1d(x,y,kind=3)
y3=f(x2)

y2 and y3 differ!

Regards
Johann


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