R/get_CRU_stack.R

In getCRUCLdata: 'CRU' 'CL' v. 2.0 Climatology Client

#' @title Download and Create a List of Raster Stack Objects From CRU CL v. 2.0 Climatology Variables
#'
#'@description This function automates downloading and importing CRU CL v. 2.0
#' climatology data into \R and creates a list of raster stacks of the
#' data.  If requested, minimum and maximum temperature may also be
#' automatically calculated as described in the data readme.txt file.  Data may
#' be cached for later use by this function, saving time downloading files in
#' future use of the function.
#'
#' Nomenclature and units from readme.txt:
#' \describe{
#' \item{pre}{precipitation (millimetres/month)}
#'   \describe{
#'     \item{cv}{cv of precipitation (percent)}
#'   }
#' \item{rd0}{wet-days (number days with >0.1mm rain per month)}
#' \item{tmp}{mean temperature (degrees Celsius)}
#' \item{dtr}{mean diurnal temperature range (degrees Celsius)}
#' \item{reh}{relative humidity (percent)}
#' \item{sunp}{sunshine (percent of maximum possible (percent of day length))}
#' \item{frs}{ground-frost (number of days with ground-frost per month)}
#' \item{wnd}{10 metre windspeed (metres/second)}
#' \item{elv}{elevation (automatically converted to metres)}
#' }
#' For more information see the description of the data provided by CRU,
#' \url{https://crudata.uea.ac.uk/cru/data/hrg/tmc/readme.txt}
#'
#' @param pre Logical.  Fetch precipitation (millimetres/month) from server and
#' return in the data frame?  Defaults to \code{FALSE}.
#' @param pre_cv Logical.  Fetch cv of precipitation (percent) from server and
#' return in the data frame?  Defaults to \code{FALSE}.  NOTE.  Setting this to
#' \code{TRUE} will always results in \strong{pre} being set to \code{TRUE} and
#' returned as well.
#' @param rd0 Logical.  Fetch wet-days (number days with >0.1millimetres rain
#' per month) and return in the data frame? Defaults to \code{FALSE}.
#' @param dtr Logical.  Fetch mean diurnal temperature range (degrees Celsius)
#' and return it in the data frame?  Defaults to \code{FALSE}.
#' @param tmp Logical.  Fetch temperature (degrees Celsius) and return it in the
#' data frame?  Defaults to \code{FALSE}.
#' @param tmn Logical.  Calculate minimum temperature values (degrees Celsius)
#' and return it in the data frame?  Defaults to \code{FALSE}.
#' @param tmx Logical.  Calculate maximum temperature (degrees Celsius) and
#' return it in the data frame?  Defaults to \code{FALSE}.
#' @param reh Logical.  Fetch relative humidity and return it in the data frame?
#' Defaults to FALSE.
#' @param sunp Logical.  Fetch sunshine, percent of maximum possible (percent of
#' day length) and return it in data frame?  Defaults to \code{FALSE}.
#' @param frs Logical. Fetch ground-frost records (number of days with ground-
#' frost per month) and return it in data frame?  Defaults to \code{FALSE}.
#' @param wnd Logical.  Fetch 10m wind speed (metres/second) and return it in
#' the data frame? Defaults to \code{FALSE}.
#' @param elv Logical.  Fetch elevation (converted to metres) and return it in
#' the data frame?  Defaults to \code{FALSE}.
#' @param cache Logical.  Store CRU CL v. 2.0 data files locally for later use?
#' If \code{FALSE}, the downloaded files are removed when R session is closed.
#' To take advantage of cached files in future sessions, use \code{cache = TRUE}
#' after the initial download and caching.  Defaults to \code{FALSE}.
#'
#' @examples
#' \donttest{
#' # Download data and create a raster stack of precipitation and temperature
#' # without caching the data files
#' CRU_pre_tmp <- get_CRU_stack(pre = TRUE, tmp = TRUE)
#'
#' CRU_pre_tmp
#' }
#'
#' @seealso
#' \code{\link{create_CRU_stack}}
#' \code{\link{manage_cache}}
#'
#' @return A \code{\link[base]{list}} of \code{\link{raster}}
#' \code{\link[raster]{stack}} objects of CRU CL v. 2.0 climatology elements
#'
#' @author Adam H. Sparks, \email{adamhsparks@@gmail.com}
#'
#' @note
#' This package automatically converts elevation values from kilometres to
#' metres.
#'
#' This package crops all spatial outputs to an extent of ymin = -60, ymax = 85,
#' xmin = -180, xmax = 180.  Note that the original wind data include land area
#' for parts of Antarctica, these data are excluded in the raster stacks
#' generated by this function.
#'
#' @export get_CRU_stack

get_CRU_stack <-
  function(pre = FALSE,
           pre_cv = FALSE,
           rd0 = FALSE,
           tmp = FALSE,
           dtr = FALSE,
           reh = FALSE,
           tmn = FALSE,
           tmx = FALSE,
           sunp = FALSE,
           frs = FALSE,
           wnd = FALSE,
           elv = FALSE,
           cache = FALSE) {
    if (!isTRUE(pre) & !isTRUE(pre_cv) & !isTRUE(rd0) & !isTRUE(tmp) &
        !isTRUE(dtr) & !isTRUE(reh) & !isTRUE(tmn) & !isTRUE(tmx) &
        !isTRUE(sunp) & !isTRUE(frs) & !isTRUE(wnd) & !isTRUE(elv)) {
      stop("\nYou must select at least one element for download.\n",
           call. = FALSE)
    }

    cache_dir <- .set_cache(cache)

    files <- .get_CRU(pre,
                      pre_cv,
                      rd0,
                      tmp,
                      dtr,
                      reh,
                      tmn,
                      tmx,
                      sunp,
                      frs,
                      wnd,
                      elv,
                      cache_dir)

    if (isTRUE(pre_cv)) {
      pre <- TRUE
    }

    s <- .create_stacks(tmn, tmx, tmp, dtr, pre, pre_cv, files)
    return(s)
  }