helper function: transform TTE ADaM data to suitable input for survival R package
ext_tte_transfer(dd, time_scale = "months", trt = NULL)
a data frame that can be used as input to survival::Surv
data frame, ADTTE read via haven::read_sas
a character string, 'years', 'months', 'weeks' or 'days', time unit of median survival time
values to include in treatment column