On Tue, 16 May 2006, Birgit Rauchenschwandtner wrote:
help
Hello,
I´m a statistic student in Austria and I have to do a survival analysis in R
by using psplines as regressor. My problem is that I sometimes (I think it
depends on the choose of the parameters) get a error message, but I do not
know what it means. After that I tried the procedure with an example dataset
R is providing. Although using the cancer dataset I also get this message.
Input: survreg(Surv(time, status) ~ pspline(age,degree=0,nterm=4), cancer)
Output: Fehler in if (!doing.well && old$half < 2) { :
Fehlender Wert, wo TRUE/FALSE nötig ist
Since the default value of df in pspline is 4 this is the same as
pspline(age,df=4,degree=0,nterm=4)
That is, you are asking for 4 (df) degrees of freedom from a spline with
only 4 (nterms) basis functions, which isn't possible.
Changing this to pspline(age,df=4,degree=0,nterm=5) works, but still is
not very useful. The point of using penalized splines rather than
ordinary regression splines is lost if you don't penalize them. I also
don't understand why you want degree=0 splines, but they will work if you
allow more basis functions than degrees of freeedom.
The error message could be more helpful, and I will change it.
-thomas
Thomas Lumley Assoc. Professor, Biostatistics
[EMAIL PROTECTED] University of Washington, Seattle______________________________________________
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