R/ymonsum.R

In cmsafops: Tools for CM SAF NetCDF Data

#'Determine multi-year monthly sums.
#'
#'The function determines multi-year monthly sums from data of a single CM SAF
#'NetCDF input file.
#'
#'@param var Name of NetCDF variable (character).
#'@param infile Filename of input NetCDF file. This may include the directory
#'  (character).
#'@param outfile Filename of output NetCDF file. This may include the directory
#'  (character).
#'@param nc34 NetCDF version of output file. If \code{nc34 = 3} the output file will be
#'  in NetCDFv3 format (numeric). Default output is NetCDFv4.
#'@param overwrite logical; should existing output file be overwritten?
#'@param verbose logical; if TRUE, progress messages are shown
#'@param nc Alternatively to \code{infile} you can specify the input as an
#'  object of class `ncdf4` (as returned from \code{ncdf4::nc_open}).
#'
#'@return A NetCDF file including a time series of multi-year monthly sums is
#'  written.
#'@export
#'
#'@family monthly statistics
#'
#' @examples
#'## Create an example NetCDF file with a similar structure as used by CM
#'## SAF. The file is created with the ncdf4 package.  Alternatively
#'## example data can be freely downloaded here: <https://wui.cmsaf.eu/>
#'
#'library(ncdf4)
#'
#'## create some (non-realistic) example data
#'
#'lon <- seq(5, 15, 0.5)
#'lat <- seq(45, 55, 0.5)
#'time <- seq(as.Date("2000-01-01"), as.Date("2010-12-31"), "month")
#'origin <- as.Date("1983-01-01 00:00:00")
#'time <- as.numeric(difftime(time, origin, units = "hour"))
#'data <- array(0:250, dim = c(21, 21, 132))
#'
#'## create example NetCDF
#'
#'x <- ncdim_def(name = "lon", units = "degrees_east", vals = lon)
#'y <- ncdim_def(name = "lat", units = "degrees_north", vals = lat)
#'t <- ncdim_def(name = "time", units = "hours since 1983-01-01 00:00:00",
#'  vals = time, unlim = TRUE)
#'var1 <- ncvar_def("SDU", "h", list(x, y, t), -1, prec = "short")
#'vars <- list(var1)
#'ncnew <- nc_create(file.path(tempdir(),"CMSAF_example_file.nc"), vars)
#'ncvar_put(ncnew, var1, data)
#'ncatt_put(ncnew, "lon", "standard_name", "longitude", prec = "text")
#'ncatt_put(ncnew, "lat", "standard_name", "latitude", prec = "text")
#'nc_close(ncnew)
#'
#'## Determine the multi-year monthly sum of the example CM SAF NetCDF
#'## file and write the output to a new file.
#'ymonsum(var = "SDU", infile = file.path(tempdir(),"CMSAF_example_file.nc"), 
#'  outfile = file.path(tempdir(),"CMSAF_example_file_ymonsum.nc"))
#'
#'unlink(c(file.path(tempdir(),"CMSAF_example_file.nc"), 
#'  file.path(tempdir(),"CMSAF_example_file_ymonsum.nc")))
ymonsum <- function(var, infile, outfile, nc34 = 4, overwrite = FALSE, verbose = FALSE, nc = NULL) {
  ymonx_wrapper(4, var, infile, outfile, nc34, overwrite, verbose, nc = nc)
}