Expects as days since admission:
- survival.length_of_stay- length of stay until discharge or death (NA if still in hosptial),
- survival.uncensored_time_to_death- time until death (NA if alive at last obs),
- survival.last_observed_event- last time patient observed alive.
Details
Calculates
- a 30 day survival duration and censoring status for survfit 
- a 1 year survival duration and censoring status for survfit 
- Hospital length of stay and censoring status for survfit 
- Categorical length of stay and 30 day survival 0-3, 4-6, 7-13, 14-29, gte 30 
Survival data will be of the form:
survival.30_day_death_xxx, survival.1_yr_death_xxx, survival.30_day_discharge
xxx_time: for this is the follow up time to event in days (max 30 or 365).
xxx_event: The event type indicator
- 0 = alive at event (censored), 
- 1 = dead. 
or for length of stay:
- 0 = still inpatient / died (censored), 
- 1 = discharged from hospital 
A survival model will be of the form:
survival::Surv(time = xxx_time, event=xxx_event) ~ ...