R/age_calc.R

In filipwastberg/filipp: My personal package with functions

#' Age calucaltion function
#' 
#' param dob date of birth
#' param enddate date to calculate difference from
#' param units "days", "months", "years"
#' 

age_calc <- function(dob, enddate = Sys.Date(), units = 'months'){
  if (!inherits(dob, "Date") | !inherits(enddate, "Date"))
    stop("Both dob and enddate must be Date class objects")
  start <- as.POSIXlt(dob)
  end <- as.POSIXlt(enddate)
  
  years <- end$year - start$year
  if(units == 'years'){
    result <- ifelse((end$mon < start$mon) | 
                       ((end$mon == start$mon) & (end$mday < start$mday)),
                     years - 1, years)    
  } else if(units == 'months'){
    months <- (years-1) * 12
    result <- months + start$mon
  } else if(units == 'days'){
    result <- difftime(end, start, units = 'days')
  } else{
    stop("Unrecognized units. Please choose years, months, or days.")
  }
  return(result)
}