R/modifyNcdfDefAtts.R

In bgctw/ncdfTools: Handling NetCDF Files

modifyNcdfDefAtts <- function(
  ### define several ncdf attributes at once
  file.con      ##<< a NetCDF object pointing to the respective ncdf file.
  , var.id      ##<< the variable id (integer) or name (string) for which to 
  ## define attributes.
  , atts        ##<< list: the attributes to define (see details or an example).
) {
  ##details<<
  ## Easily define a couple of attributes for a single ncdf variable in one step.
  ##details<<
  ## The atts attribute should be a list with as many elements as attributes 
  ## should be added to the
  ## variable in the ncdf file. The names of the attributes are taken from the 
  ## names of the
  ## elements of this list and the attribute values are defined by the values 
  ## of the list elements.
  ## The type/class of the attribute (values) is determined automatically.
  #
  ##seealso<<
  ##\code{\link[RNetCDF]{att.put.nc}}
  n.steps       <- length(atts)
  att.names     <- names(atts)
  ind.fillvalue <- na.omit(match(c('_FillValue', 'missing_value'), att.names))
  if (length(ind.fillvalue) == 1) {
    att.t      <- c('_FillValue', 'missing_value')[
      !is.element(c('_FillValue', 'missing_value'), att.names)]
    att.names  <- c(att.names, att.t)
    atts       <- c(atts, atts[[ind.fillvalue]])
    names(atts)[length(atts)] <- att.t
    n.steps          <- n.steps + 1
  }
  for (i in 1:n.steps) {
    att.value        <- atts[[i]]
    if (is.numeric(att.value)) {
      if (att.names[i] == '_FillValue' | att.names[i] == 'missing_value') {
        att.type <- var.inq.nc(file.con, var.id)$type
      } else {
        att.type <- 'NC_DOUBLE'
      }
    } else {
      att.type     <- 'NC_CHAR'
    }
    att.put.nc(file.con, var.id, att.names[i], att.type, att.value)
  }
}
attr(modifyNcdfDefAtts, "ex") <- function() {
  attributes.define <- list(
    LongName = 'This is the long name',
    missingValue = -99999,
    units = 'm/s')
  ## needs an open connection to a valid ncdf file pointed to by file.con
  file.con   <- RNetCDF::create.nc(file.path(tempdir(),'test.nc'))
  RNetCDF::dim.def.nc(file.con, 'testdim')
  RNetCDF::var.def.nc(file.con, 'test', 'NC_CHAR', 'testdim')
  modifyNcdfDefAtts(file.con, 'test', atts = attributes.define)
  ## show all attributes
  infoNcdfAtts(file.con, 'test')
  RNetCDF::close.nc(file.con)
}