[R] Whitehead's group sequential procedures

[Emmanuel Charpentier]

Dear List,

I would like to know if there exist some R implementation of John 
Whitehead's procedures for the planning and analysis of group sequential 
clinical trials. His book is enlightenig but somewhat frustrating : it 
has a good basic exposition of his framework, but the technical details 
are sparse, and leave much work to do when one plans to reuimplement 
part of the procedures. For example, one has to work out the computation 
of test regions in non-trivial cases, the P-value and  confidence 
interval building, etc ... Given my abilities, I'd rather *not* do this ...

Did someone implement these procedures in R ? I am aware of a 
(commercial) implementation in S+, but Googling for an R implementation 
(and looking in the r-help archive) was ... well ... frustrating.

If no one did, and there is some interest, I might try to derive the 
necessary steps and reimplement this.

Sincerely,

					Emmanuel Charpentier

PS : please Cc: me your answers, since I'm not on the list and reading 
it through the archives.
-- 
Emmanuel Charpentier			Tel : +33-(0)1 40 27 35 98
Secrétariat Scientifique du CEDIT	Fax : +33-(0)1 40 27 55 65
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