outcome_by_followup_time: Cohort outcome by follow-up time
In JayAchar/hisreportr: hisreportr: Automating MSF OCA EMR reporting

Calculate each patient's cohort status at any timepoint since treatment initiation by defining a reporting date and follow-up time in months

outcome_by_followup_time(
  followup_month,
  df,
  reporting_date,
  start_var,
  date_var,
  id_var,
  status_var
)

`followup_month`	integer defining the follow-up time in months
`df`	data frame of cohort status changes
`reporting_date`	date defining the reporting date
`start_var`	character defining the name of the start treatment variable
`date_var`	character defining the status change date variable
`id_var`	character defining the patient ID variable
`status_var`	character definintg the status change variable