On Nov 17, 2010, at 1:05 PM, Federico Calboli wrote:
Hi All,
I am trying to figure out how to get the position of the knots in a
pspline used in a cox model.
As far as I understand it, the term "knot" should be used with natural
splines, but not for penalized smoothing splines. See p 124 of
Therneau and Gramsch for better description and illustrations. If you
want to see the weighting of a particular pspline then this example
may help:
nn=rnorm(20)
matrix(pspline(nn), nrow=20)[order(nn), ]
# sorts the spline basis weights so the overlap is "visible"
--
David.
my.model = coxph(Surv(agein, ageout, status) ~ pspline(x), mydata) #
x being continuous
How do I find out where the knot of the spline are? I would like to
know to figure out how many cases are there between each knot.
Best,
Federico
--
Federico C. F. Calboli
Department of Epidemiology and Biostatistics
Imperial College, St. Mary's Campus
Norfolk Place, London W2 1PG
Tel +44 (0)20 75941602 Fax +44 (0)20 75943193
f.calboli [.a.t] imperial.ac.uk
f.calboli [.a.t] gmail.com
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