Survival

surv_cat() :
Details see Readme
Revert "Survival"

This reverts commit 62c11227a37a56c79457f1132b5b40a7c8b4b222.
Revert "Revert "Survival""

This reverts commit da68cef7b53ed4e17ef2076f06862e299c4b1d2d.