On 02/16/2013 05:00 AM, r-help-request at r-project.org
wrote:> Then I perform cox regression as follows
> m2_1<-coxph(Surv(X_t0,X_t, vlsupp) ~ nvp + as.factor(cd4pccat) +
> as.factor(vlcat) + as.factor(agecat) + as.factor(whostage) +
> as.factor(hfacat) + as.factor(wfacat) + as.factor(wfhcat) +
> as.factor(resistance) + as.factor(postrantb) +
>
cluster(id),data=myimp$imputations[[1]],method="breslow",robust=TRUE)
> summary(m2_1)
> The I get the following eWarning message:
> In fitter(X, Y, strats, offset, init, control, weights = weights, :
> Ran out of iterations and did not converge
Failure to converge is highly unusual for coxph unless the model is near
singular. A good
rule for Cox models is to have 10-20 events for each coefficient. When models
get below
2 events/coef the results can be unreliable, both numerically and biologically,
and some
version of a shrinkage model is called for. What are the counts for your data
set?
A vector of inital values, if supplied, needs to be of the same length as the
coefficients. Make it the same length and in the same order as the printed
coefficients
from your run that did not converge.
Terry Therneau