Suppose I have a dataset contain three variants, looks like
> head(dta)
Sex tumorsize Histology time status
0 1.5 2 12.1000 0
1 1.8 1 38.4000 0
.....................
Sex: 1 for male; 0 for female., two levels
Histology: 1 for SqCC; 2 for High risk AC; 3 for low risk AC, three levels
Now I need to get a Time-dependent coefficients cox fit:
library(survival)
for(i in c(1,3) dta[,i] <- factor(dta[,i])
fit <-
coxph(
Surv(time, status) ~ Sex + tumorsize + Histology + tt(Histology),
data = dta,
tt = function(x, t, ...) x * log(t)
)
But I keep gettting this error says:
Error in if (any(infs)) warning(paste("Loglik converged before variable ", :
missing value where TRUE/FALSE needed
In addition: Warning message:
In Ops.factor(x, log(t)) : ‘*’ not meaningful for factors.
How can I fix it? I know that the "Sex" and "Histology" are both
categorical variants. I want to have a model that have two β(t) = a +
blog(t) for each histology level.
Thank you！
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