R/cmsaf.div.R

In cmsafops: Tools for CM SAF NetCDF Data

#'Divide the fields of two input NetCDF files.
#'
#'The function divides the fields of infile1 by the fields of infile2. Infiles have
#'to have the same spatial and temporal dimension or one infile can contain only
#'one timestep. The outfile uses the meta data of infile1.
#'
#'@aliases div
#'
#'@param var1  Name of variable in infile1 (character).
#'@param var2  Name of variable in infile2 (character).
#'@param infile1 Filename of first input NetCDF file. This may include the
#'  directory (character).
#'@param infile2 Filename of second 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 nc1 Alternatively to \code{infile1} you can specify the input as an
#'  object of class `ncdf4` (as returned from \code{ncdf4::nc_open}).
#'@param nc2 Alternatively to \code{infile2} you can specify the input as an
#'  object of class `ncdf4` (as returned from \code{ncdf4::nc_open}).
#'
#'@return A NetCDF file including the divided fields of infile1 and infile2 is
#'  written.
#'@export
#'
#'@family mathematical operators
#'
#' @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(10, 15, 0.5)
#'lat <- seq(50, 55, 0.5)
#'time <- c(as.Date("2000-01-01"), as.Date("2001-02-01"))
#'origin <- as.Date("1983-01-01 00:00:00")
#'time <- as.numeric(difftime(time, origin, units = "hour"))
#'data1 <- array(250:350, dim = c(11, 11, 1))
#'data2 <- array(230:320, dim = c(11, 11, 1))
#'
#'## create two example NetCDF files
#'
#'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[1], unlim = TRUE)
#'var1 <- ncvar_def("SIS", "W m-2", list(x, y, t), -1, prec = "short")
#'vars <- list(var1)
#'ncnew <- nc_create(file.path(tempdir(),"CMSAF_example_file_1.nc"), vars)
#'ncvar_put(ncnew, var1, data1)
#'ncatt_put(ncnew, "lon", "standard_name", "longitude", prec = "text")
#'ncatt_put(ncnew, "lat", "standard_name", "latitude", prec = "text")
#'nc_close(ncnew)
#'
#'t <- ncdim_def(name = "time", units = "hours since 1983-01-01 00:00:00",
#'  vals = time[2], unlim = TRUE)
#'ncnew <- nc_create(file.path(tempdir(),"CMSAF_example_file_2.nc"), vars)
#'ncvar_put(ncnew, var1, data2)
#'ncatt_put(ncnew, "lon", "standard_name", "longitude", prec = "text")
#'ncatt_put(ncnew, "lat", "standard_name", "latitude", prec = "text")
#'nc_close(ncnew)
#'
#'## Divide the fields of both example CM SAF NetCDF files and write the
#'## result into one output file.
#'cmsaf.div(var1 = "SIS", var2 = "SIS", infile1 = file.path(tempdir(),
#'  "CMSAF_example_file_1.nc"), infile2 = file.path(tempdir(),
#'  "CMSAF_example_file_2.nc"), outfile = file.path(tempdir(),
#'  "CMSAF_example_file_div.nc"))
#'
#'unlink(c(file.path(tempdir(),"CMSAF_example_file_1.nc"), 
#'  file.path(tempdir(),"CMSAF_example_file_2.nc"),
#'  file.path(tempdir(),"CMSAF_example_file_div.nc")))
cmsaf.div <- function(var1, var2, infile1, infile2, outfile, nc34=4,
                      overwrite = FALSE, verbose = FALSE, nc1 = NULL, nc2 = NULL) {
  arith_wrapper(4, var1, var2, infile1, infile2, outfile, nc34, overwrite, verbose, nc1 = nc1, nc2 = nc2)
}