u/Bikes_are_amazing

Lets say I've done Cox regression with the lung dataset and adjusted the model for an age category, and I want to check if the PH assumption holds. If it's an unadjusted model you can do a log minus log plot of the Kaplan-Meier curve, but is this still possible to use the log minus log method to check the PH assumption if the model is adjusted?

Thanks in advance.

Example code below:

library(tidyverse)
library(survival)

lung <- lung %>% 
  mutate(sex = if_else(sex == 1 , "Man" , "Woman")) %>% 
  mutate(age_cat = if_else(age < 60 , "<60", ">=60"))

cox_fit <- coxph(Surv(time,status) ~ sex + age_cat , data = lung)