Model specification

[adibender]

@fabian-s I think its time to think more generally about how we call the functions for data transformation.

• Right now we use Surv(time, status)~ ... + ... | cumulative(...),
  although the Surv(time, status) part is only a mirrage, as we don't really do anything Surv specific with it, except extracting the event time and status variables, while the usual functionality of Surv() is not supported, e.g.

• Surv(time, status == 2) ~ ... (see also More robust split_data function #31) or

• Surv(time1, time2, status) ~ ... e.g. for left truncated data,

• etc.

This will also be relevant when/if we extend the functionality to competing risks/multistate models, in which case we need to support calls like

as_ped(Surv(time, event1) | Surv(time, event2) ~ lin_pred_event1 | lin_pred_event2

This could be done nicely using the Formula functionality, but we already use | on the RHS to differentiate between cumulative effects and "normal" effects ~ ... + ... | cumulative().
The latter may not be necessary, as we can simply extract cumulative via the specials function?

[fabian-s]

hey, you're on a roll today..... 😮

agree, using specials and having multiple RHS via Formula seems like the way to go, let's try to have as few idiosyncrasies as possible.

need to think more about possible/allowed input data formats as well -- are different event types going to be recorded in different columns (one time column per event type) or in a pair of columns (time, event) with potentially multiple entries per subject? for the first, we'd need multiple RHS, for the second, we could use the event column as "status".

[adibender]

We also have to consider different types of censoring/truncation on the LHS

[adibender]

I'll close this general issue. Open individual issues for specific cases