[R] survey package: weights used in svycoxph()
Vinh Nguyen
vqnguyen at uci.edu
Tue May 18 02:27:54 CEST 2010
Dear R-help,
Let me know if I should email r-devel instead of this list. This
message is addressed to Professor Lumley or anyone familiar with the
survey package.
Does svycoxph() implement the method outlined in Binder 1992 as
referenced in the help file? That is, are weights incorporated in the
ratio term (numerator and denominator) of the estimating equation? I
don't believe so since svycoxph() calls coxph() of the survival
package and weights are applied once in the estimating equation. If
the weights are implemented in the ratio, could you point me to where
in the code this is done? I would like to estimate as in Binder but
with custom weights. Thanks.
This is mentioned in the help file but I don't quite understand:
The main difference between svycoxph function and the robust=TRUE
option to coxph in the
survival package is that this function accounts for the reduction in
variance from stratified sampling
and the increase in variance from having only a small number of clusters.
Vinh
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