R/find_weekday.R

In nelsonroque/m2c2R: Scoring and Summarizing of Cognitive task data from the Mobile Monitoring of Cognitive Change Project (M2C2).

#' m2c2R
#' @name find_weekday
#' 
#' @author Nelson Roque, \email{Nelson.Roque@@ucf.edu}
#' 
#' @export
#' @param wday Abbreviation for starting day ("sun", "mon", "tues", "wed", "thurs", "fri", "sat")
#' @param days Number of days to increment
#' @param weekstart Day considered as the start of the week (either Sunday or Monday)
#' @details This function takes a day of the week and a number of days to increment as input
#' and returns the name of the weekday that is n days after the wday provided. 
#' @return Returns the name of the weekday that is n days after the wday provided.
find_weekday <- function(wday="sun", days = 1, weekstart = "sun") {
  if(days > 7) {
    stop("Error. Support not available for jittering more than 7 days")
  }
  
  # determine week start by user input
  if(weekstart == "sun") {
    days_table = c("sun", "mon", "tues", "wed", "thurs", "fri", "sat")
  } else {
    days_table = c("mon", "tues", "wed", "thurs", "fri", "sat", "sun")
  }
  
  # check current index
  index_of_current_day = which(days_table == wday)
  
  # increment to sought day
  index_of_next_day = index_of_current_day + days
  
  # check range of next day
  if(index_of_next_day > 7){
    ver_index_of_next_day = index_of_next_day - 7
    ver_index_of_next_day_label = days_table[ver_index_of_next_day]
  } else {
    ver_index_of_next_day = index_of_next_day
    ver_index_of_next_day_label = days_table[ver_index_of_next_day]
  }
  
  return(ver_index_of_next_day_label)
}