cmsaf (version 1.9.5)

seltime: Extract specific timestep.

Description

This function selects a given list of times from a timeseries.

Usage

seltime(var, hour_min, infile, outfile, nc34)

Arguments

var

Name of NetCDF variable (character).

hour_min

Times, which should be selected, in form of a vector of character values in the form of 'HH:MM:SS' (e.g. c('12:00:00') (character).

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=4 the output file will be in NetCDFv4 format (numeric). Default output is NetCDFv3.

Value

A NetCDF file including a timeseries of the selected times is written.

Examples

# NOT RUN {
## 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(ISOdate(2000,1,1), ISOdate(2000,1,6), 'hours')
  origin <- as.Date('1983-01-01 00:00:00')
  time <- as.numeric(difftime(time,origin,units='hour'))
  data <- array(250:350,dim=c(21,21,121))

## 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('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 12:00 and 21:00  values of the example CM SAF NetCDF  
## file and write the output to a new file.
   seltime('SIS',c('12:00:00','21:00:00'),'CMSAF_example_file.nc', 
   'CMSAF_example_file_seltime.nc')
# }