Rwtd

Rough R translation of functions from the Stata wtdttt package

(c) 2023 Malcolm Gillies malcolm.gillies@unsw.edu.au

This code is a direct translation of portions from the Stata module wtdttt, available at: https://econpapers.repec.org/software/bocbocode/s458265.htm by Katrine Bødkergaard Nielsen (kani@ph.au.dk) and Henrik Støvring (stovring@ph.au.dk)

These functions estimate parameters of the ordinary and reverse Waiting Time Distribution (WTD) by maximum likelihood, with application to modelling the recurrence of drug dispensing. Please see the Stata package documentation for references.

As with wtdttt, this code is made available under the terms of the GPL v3 (or later).

Currently, only the lognormal distribution is implemented.

Example data in Stata format, taken directly from the wtdttt package, is included for demonstration purposes

library(haven)

x <- read_dta("ref/wtddat_dates.dta")

x.w <- wtdttt(x$rx1time, as.Date('2014-01-01'), as.Date('2014-12-31'),
      reverse=F)

summary(x.w)

x <- read_dta("ref/ranwtddat_discdates.dta")

x.w <- ranwtdttt(x$rxdate, x$pid, as.Date('2014-01-01'),
      as.Date('2014-12-31'), reverse=F)

summary(x.w)

x.w <- ranwtdttt(x$rxdate, x$pid, as.Date('2014-01-01'), as.Date('2014-12-31'),
    reverse=T)

summary(x.w)