Hello,

I'm trying to estimate a cox model with a frailty variable and time-dependent covariate (below there is the statement I use and the error message). It's seems to be impossible, because every time I add the time-dependent covariate the model doesn't converge. Instead, if I estimate the same model without the time-dependent covariate it's converge. I'd like knowing if it's a statistical problem due to the model formula or if it could be a problem related to my data.

Thanks a lot

Emanuela Rossi


> fit_19_1<-coxph(Surv(DATA_INI1,DATA_FIN1,EVENT1)~ V1+V2+alt1+alt2+strata(autocorr1)+cap1+SP+SP2+SP3+SP3:log(DATA_FIN1)+D1500+D3000+D4500+frailty.gaussian(ID),data=SURV1)

Warning messages: 
1: Inner loop failed to coverge for iterations 1 3 in: coxpenal.fit(X, Y, strats, offset, init = init, control, weights = weights,  
2: longer object length
        is not a multiple of shorter object length in: offset + coxfit$fcoef[x[, fcol]] 
3: X matrix deemed to be singular; variable 8 in: coxph(Surv(DATA_INI1, DATA_FIN1, EVENT1) ~ V1 + V2 + alt1 + alt2 +  

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