R/dynamic_proj_dates.R

In dynamicSDM: Species Distribution and Abundance Modelling at High Spatio-Temporal Resolution

#'Generate vector of dates for dynamic projections
#'
#'Creates a vector of dates at regular intervals between two given dates.
#'@param startdate a character string, the start date in format "YYYY-MM-DD".
#'@param enddate a character string, the end date in format "YYYY-MM-DD".
#'@param interval.level a character string, the time-step of intervals. One of `day`,`week`, `month`
#'  or `year`: can be abbreviated.
#'@param interval a numeric value, the length of interval in `interval.level` units to generate
#'  between the start and end date.
#'@details Function returns a vector of dates between `start.date` and `end.date` at given interval
#'  size.
#'@return Vector of dates between start date and end date split at regular intervals.
#' @examples
#' dynamic_proj_dates(
#'  startdate = "2000-01-01",
#'  enddate = "2001-01-01",
#'  interval.level = "month",
#'  interval = 2
#')
#'@export
#'

dynamic_proj_dates <-  function(startdate,
                                enddate,
                                interval.level,
                                interval) {

    # Match interval.level to available options
    interval.level <- match.arg(arg = interval.level,
                                choices = c("day", "week", "month", "year"))

    # Check formatting of input arguments
    if (!is.character(startdate)) {stop("startdate must be character")}
    if (!is.character(enddate)) {stop("enddate must be character")}

    # Check dates given are valid dates
    tryCatch({lubridate::as_date(startdate)}, warning = function(e) {
      stop("Invalid startdate")})

    tryCatch({lubridate::as_date(enddate)}, warning = function(e) {
      stop("Invalid enddate")})

    startdate <- as.Date(startdate)
    enddate <- as.Date(enddate)

    # Check start date is earlier than end date
    if (startdate - enddate > 0) {stop("startdate must be before enddate")}

    if (startdate - enddate == 0) {

      message("startdate and enddate are equal, returning single date")

      return(as.character(startdate))

      }


    listofdates <- as.Date(startdate)

    if (interval.level == "day") {
      i <- lubridate::interval(startdate, enddate) %/% lubridate::days(interval)
      if (i == 0) {stop("There are no dates for given interval and end date")}

      # Iterate through number of interval dates, adding the interval each time
      for (int in 1:i) {
        listofdates <- c(listofdates, (startdate + lubridate::days((int * interval))))
      }

    }

    if (interval.level == "week") {
      i <- lubridate::interval(startdate, enddate) %/% lubridate::weeks(interval)
      if (i == 0) {stop("There are no dates for given interval and end date")}

      # Iterate through number of interval dates, adding the interval each time
      for (int in 1:i) {
        listofdates <- c(listofdates, (startdate + lubridate::weeks((int * interval))))
      }
    }

    if (interval.level == "month") {
      i <- lubridate::interval(startdate, enddate) %/% months(interval)

      if (i == 0) {stop("There are no dates for given interval and end date")}

      # Iterate through number of interval dates, adding the interval each time
      for (int in 1:i) {
        listofdates <- c(listofdates, (startdate + months((int * interval))))
      }
    }

    if (interval.level == "year") {
      i <- lubridate::interval(startdate, enddate) %/% lubridate::years(interval)
      if (i == 0) {stop("There are no dates for given interval and end date")}

      # Iterate through number of interval dates, adding the interval each time
      for (int in 1:i) {
        listofdates <- c(listofdates, (startdate + lubridate::years((int * interval))))
      }
    }

    return(listofdates)
  }