extract.period {cmsafops}

Remove a time period.

Description

This function deletes a time period between a given start and end date from a time series. If start and end are the same, only this date will be removed.

Usage

extract.period(
  var,
  start,
  end,
  infile,
  outfile,
  nc34 = 4,
  overwrite = FALSE,
  verbose = FALSE,
  nc = NULL
)

Arguments

var

Name of NetCDF variable (character).

start

Start date as character in form of 'YYYY-MM-DD' (e.g., '2001-12-31').

end

End date as character in form of 'YYYY-MM-DD' (e.g., '2014-01-01').

infile

Filename of 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

nc

Alternatively to infile you can specify the input as an object of class ncdf4 (as returned from ncdf4::nc_open).

Value

A NetCDF file excluding the selected time period is written.

See Also

Other selection and removal functions: extract.level(), sellonlatbox(), selmon(), selperiod(), selpoint(), selpoint.multi(), seltime(), selyear()

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(250:350, 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("SIS", "W m-2", 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)

## Remove a 13-months period of the example CM SAF NetCDF file and write
## the output to a new file.
extract.period(var = "SIS", start = "2001-01-01", end = "2002-01-01", 
 infile = file.path(tempdir(),"CMSAF_example_file.nc"),
 outfile = file.path(tempdir(),"CMSAF_example_file_extract.period.nc"))

unlink(c(file.path(tempdir(),"CMSAF_example_file.nc"), 
 file.path(tempdir(),"CMSAF_example_file_extract.period.nc")))