cmsafops: timcovar – R documentation

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timcovar

Determine covariances over time.

Description

The function determines covariances over time from data of two CM SAF NetCDF input files. This function is applicable to 3-dimensional NetCDF data.

Usage

timcovar(
  var1,
  infile1,
  var2,
  infile2,
  outfile,
  nc34 = 4,
  overwrite = FALSE,
  verbose = FALSE
)

Arguments

`var1`	Name of NetCDF variable of the first data set (character).
`infile1`	Filename of first input NetCDF file. This may include the directory (character).
`var2`	Name of NetCDF variable of the second data set (character).
`infile2`	Filename of second input NetCDF file. This 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 a time series of covariances over time is written.

Examples

## Create two example NetCDF files with a similar structure as used by CM
## SAF. The files are 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 <- as.Date("2000-05-31")
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 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("SIS", "W m-2", list(x, y, t), -999, prec = "float")
vars <- list(var1)
ncnew_1 <- nc_create(file.path(tempdir(), "CMSAF_example_file_1.nc"), vars)
ncnew_2 <- nc_create(file.path(tempdir(), "CMSAF_example_file_2.nc"), vars)

ncvar_put(ncnew_1, var1, data1)
ncvar_put(ncnew_2, var1, data2)

ncatt_put(ncnew_1, "lon", "standard_name", "longitude", prec = "text")
ncatt_put(ncnew_1, "lat", "standard_name", "latitude", prec = "text")

ncatt_put(ncnew_2, "lon", "standard_name", "longitude", prec = "text")
ncatt_put(ncnew_2, "lat", "standard_name", "latitude", prec = "text")
nc_close(ncnew_1)
nc_close(ncnew_2)

## Determine the covariances over time of the example CM SAF NetCDF files and
## write the output to a new file.
timcovar(var1 = "SIS", infile1 = file.path(tempdir(),"CMSAF_example_file_1.nc"), 
      var2 = "SIS", infile2 = file.path(tempdir(), "CMSAF_example_file_2.nc"),
      outfile = file.path(tempdir(),"CMSAF_example_file_timcovar.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_timcovar.nc")))

cmsafops

Tools for CM SAF NetCDF Data

v1.1.1

GPL (>= 3)

Authors

Steffen Kothe [aut, cre]

Initial release