I suppose that any row in newdata only corresponds to a single stratum, and those survival estimates from other strata do not make sense. Maybe they are included for comparison purpose. But with survival estimates from all strata, I don't know how to retrieve survival estimates from a right stratum for each row in newdata in a simple way, particularly in a body of function where only the result of coxph is available. I am afraid that I must miss something here and the answer should be simple.
Any clues are welcome.