cmsaf.cat: Concatenate datasets of several NetCDF input files.

In cmsafops: Tools for CM SAF NetCDF Data

Concatenate datasets of several NetCDF input files.

Description

This function concatenates datasets of an arbitrary number of input files. All input files have to have the same structure with the same variable and different timesteps.

Usage

cmsaf.cat(var, infiles, outfile, nc34 = 4, overwrite = FALSE, verbose = FALSE)

Arguments

var	Name of NetCDF variable (character).
infiles	Vector with filenames of input NetCDF files. The file names may include the directory (character).
outfile	Filename of output NetCDF file. This may include the directory (character).
nc34	NetCDF version of output file. If nc34 = 3 the output file will be in NetCDFv3 format (numeric). Default output is NetCDFv4.
overwrite	logical; should existing output file be overwritten?
verbose	logical; if TRUE, progress messages are shown

Value

A NetCDF file including the merged time series is written. The resulting file uses the meta data of the first input file.

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 <- 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(21, 21, 1))
data2 <- array(230:320, dim = c(21, 21, 1))

## create two simple 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)

## Cut a region and merge both example CM SAF NetCDF files into one
## output file.  Get path information of working directory with getwd()
## command.
wd <- getwd()
cmsaf.cat(var = "SIS", infiles = c(file.path(tempdir(),
 "CMSAF_example_file_1.nc"), file.path(tempdir(),"CMSAF_example_file_2.nc")),
 outfile = file.path(tempdir(),"CMSAF_example_file_cat.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_cat.nc")))

cmsafops documentation built on Sept. 18, 2023, 5:16 p.m.