User`s guide

Nonparametric Fitting
3-71
parameter, you can consider these fits to be parametric. However, smoothing
splines are also piecewise polynomials like cubic spline or shape-preserving
interpolants and are considered a nonparametric fit type in this guide.
Note The smoothing spline algorithm used by the Curve Fitting Toolbox is
based on the
csaps function included with the Spline Toolbox. Refer to the
csaps reference pages for detailed information about smoothing splines.
The nuclear reaction data from the file
carbon12alpha.mat is shown below
with three smoothing spline fits. The default smoothing parameter (p = 0.99)
produces the smoothest curve. The cubic spline curve (p = 1) goes through all
the data points, but is not quite as smooth. The third curve (p = 0.95) misses
the data by wide margin and illustrates how small the “interesting range” of p
can be.
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
−50
0
50
100
150
200
250
300
350
angle
counts
C12Alpha
p=default
p=1
p=0.95