selyear: Extract a list of years.

In cmsafops: Tools for CM SAF NetCDF Data

Extract a list of years.

Description

This function selects a given list of years from a time series.

Usage

selyear(
  var,
  year = c(2000),
  infile,
  outfile,
  nc34 = 4,
  overwrite = FALSE,
  verbose = FALSE,
  nc = NULL
)

Arguments

var	Name of NetCDF variable (character).
year	Year in form of a comma separated vector of integer values (e.g. c(2000,2015)) (integer).
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 including a time series of the selected years is written.

See Also

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

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)

## Select all values of the year 2003 and 2006 of the example CM SAF
## NetCDF file and write the output to a new file.
  selyear(var = "SIS", year = c(2003,2006), infile = file.path(tempdir(),
  'CMSAF_example_file.nc'), outfile = file.path(tempdir(),
  'CMSAF_example_file_selyear.nc'))

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

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