Re: Newbie question: how to change netcdf header?

At 12:42 AM 10/26/2005, Roger Olivella wrote:
> Hi,
>
> I'm new in netcdf Java and I'm wondering if it's possible to change the
> netcdf header without changing the data. I've tried to do that but it
> doesn't work (v2.2.10 API):

Changing the header would generally change its size.
The variables data would follow the header in the netcdf file, so
changing the headers size would require relocating the variables data.
Operating systems don't usually support inserting/deleting into the
middle of a file, making such an operation very expensive.

Executive summary: not practical. Simpler to build a new netcdf file from
the old.


> -------------------------------------
> import java.io.*;
>
> import ucar.ma2.*;
> import ucar.nc2.*;
>
> public class test2 {
>
>  public static void main(String[] args) {
>    String filename="/home/netcdf/foo.nc";
>    try {
>
>      //Load netcdf:
>      NetcdfFileWriteable ncfile=new
> NetcdfFileWriteable(filename);
>     
>      //Modify a netcdf variable (lattitude): from
> float datatype to double datatype      
>      Variable
> varLat=ncfile.findVariable("lat");
>      varLat.setDataType(DataType.DOUBLE);//lat from
> float to double
>     
>      //ncfile.create(); -> doesn't work
>     
>      //Close:
>      ncfile.flush();
>      ncfile.close();
>
>    } catch (IOException ioe){
>      ioe.printStackTrace();
>      System.err.println("ERROR creating
> file");
>    }
> -------------------------------------
>
> I think that I'm missing a method that actally writes the changes to the
> nc file but I don't know wich is it. I've tried ncfile.create() but I've
> got "not in define mode".
>
> Any help would be appreciate.
>
> Thanks in advance,
>
> Roger Olivella

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