The splinefun documentation indicates that "natural" is one of the
types of cubic spline options available.
Does rcs actually do fitting? Such would not be my expectation on
reading the documentation and I do not see any examples of such
functionality in the help pages.
--
David Winsemius
On Mar 31, 2009, at 6:09 AM, Stephan Kolassa wrote:
Hi,
if you are looking for *natural* cubic splines (linear beyond the
outer knots), you could use rcs() in Frank Harrell's Design package.
HTH,
Stephan
David Winsemius schrieb:
If one enters:
??"spline"
... You get quite a few matches. The one in the stats functions
that probably answers your specific questions is:
"splinefun {stats} R Documentation
Interpolating Splines Description
Perform cubic (or Hermite) spline interpolation of given data
points, returning either a list of points obtained by the
interpolation or a function performing the interpolation."
"splinefun returns a function with formal arguments x and deriv,
the latter defaulting to zero. This function can be used to
evaluate the interpolating cubic spline (deriv=0), or its
derivatives (deriv=1,2,3) at the points x, where the spline
function interpolates the data points originally specified. This is
often more useful than spline."
Perhaps you need to review from you basic intro material regarding
help.search("text") # or
??"text" # possibilities.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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