strata parameter for Cox stratification

[j-bac]

It would be nice to have a parameter to stratify based on categorical variables, as is done in lifelines package
https://lifelines.readthedocs.io/en/latest/fitters/regression/CoxPHFitter.html

[melodiemonod]

Hi @j-bac ,

Thank you fo submitting an issue. Could you please provide a short code snippet to illustrate your request?

[j-bac]

The lifelines package class I linked provides a full implementation of the idea. The strata parameter allows to specify one/several categorical variable(s). This allows each group of the categorical variable to have its own baseline hazard.

I haven't looked into the exact way lifelines achieves this but I thought it might be possible to modify torchsurv's Cox loss to achieve something similar. Maybe something as simple as computing the loss separately for each group and then taking the sum