R/aggregateNcdf.R

In bgctw/ncdfTools: Handling NetCDF Files

aggregateNcdf <- function(
  ### aggregate data across time in ncdf files by calling a cdo command
  fileName             ##<< character vector: names of the files to aggregate.
  , path.out = getwd() ##<< character: path to save the results files to. 
  , period             ##<< integer or one of 'hour', 'day', 'month' or 'year': 
   ## period to aggregate to. In case
   ##   of an integer value, the unit is time steps.
) {
  ##description<<
  ## This function aggregates time periods in ncdf files. Basically it is just a
  ## wrapper around the respective cdo function.
  ##test input
  # if (!checkInstalled('cdo'))
  #   stop('cdo not found. Please install it.')
  if (inherits(period, 'character')) {
    cdoOperator <- paste(switch(period, hourly = 'hour', daily = 'day', monthly = 'mon',
                        yearly = 'year', 'not_available'), 'mean', sep = '')
    if (cdoOperator == 'not_vailable')
      stop(paste('Period \'', period, '\' not implemented!', sep = ''))
  } else if (inherits(period, 'numeric')) {
    cdoOperator      <- paste('timselmean,', period, sep = '') 
  } else {
    stop('Plase only supply numeric or character values for \'period\'!')
  }
  ## determine cdo command values
  fileNameOut <- file.path(
    path.out
    , sub('[.]nc', paste('_', period, '.nc', sep = ''), sub('.*/', '', fileName)))
  cdoCmd      <- paste('cdo ', cdoOperator, ' ', fileName, ' ', fileNameOut, sep = '')
  ##run aggregation
  system(cdoCmd)
  message('Created file ', fileNameOut)
  ##value<<
  ## character string: name of the file created. 
  invisible(fileNameOut)
}