Adjusted survival curves (Thanks to sample code: https://rpubs.com/daspringate/survival )
Thanks to Moderator/Admin's Great Work! For a successful solution I used advice that could be understood:
1. Peter Dalgaard: The code does not work, because the covariates are not factors.
2. Jeff Newmiller: "Change the columns into factors before you give them to the coxph function, e.g. df$treatment <- as.factor(df$treatment)"
And I study David Winsemius's instructions.THANKS!!!