[R] Splines under tension

[Terry Therneau]

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Does anyone know if R has a function for splines under tension. I know
there are numerous packages for spline interpolation within R i just
can't find one that lets you determine the tension factor.

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In the statistics literature these are called "smoothing splines".  For
instance the s(x) construct in gam or pspline(x) in a coxph formula.
There are multiple ways to specify the 'tension factor', many in the
statistics community prefer the 'equivalent degrees of freedom' so you
will often see df=___ in the examples.  You can also directly enter a
penalty mulitplier.  
   To get a clearer answer you would need to give the explicit
definition of "tension factor" from the literature you are quoting.
It's not just that different disciplines rediscover the same ideas, they
also relabel them.

Terry Therneau