[Scipy-tickets] [SciPy] #379: Default value of s is not as described in the documentation to splrep
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Fri Feb 23 17:39:01 CST 2007
#379: Default value of s is not as described in the documentation to splrep
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Reporter: peridot | Owner: somebody
Type: defect | Status: new
Priority: normal | Milestone:
Component: Other | Version:
Severity: normal | Keywords:
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splrep requires a smoothing parameter, s, to operate. A default value of
s, 0.001, was supplied as a response to ticket 199 but not described in
the docstring. I suggest changing the default value of s (and changing the
docstring to match, if necessary).
The value None chooses s=m-sqrt(2*m), as described in the docstring. The
effect of this setting (None) is to choose a smoothing spline instead of
an interpolating spline.
The value s=0. constructs an interpolating spline, forcing it to pass
through all the points.
The value s=0.001 produces a spline which (if no weights are provided)
tries to pass within about 0.001 of each point. This is a strange choice
for a default...
I recommend setting s=None to the default, and further modifying it so
s=None produces s=0. if no weights are provided (giving an interpolating
spline) and s=m-sqrt(2*m) if weights are provided (since the user
presumably then wanted a smoothing spline).
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Ticket URL: <http://projects.scipy.org/scipy/scipy/ticket/379>
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