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OK, next question. Exactly what are the semantics of "Unlimited"
dimensions? I assume this means that I can add data bit by bit (or
perhaps it doesn't). I'm thinking of applications where a simulation
does not know, a priori, how long it will run but I'd like to write the
data out as I go. I assume this is possible, but how would I do it.
For example, could I just list the dimension as Unlimited and then just
keep setting the data for ever increasing indices?!?
Also, I can I have more than 1 unlimited dimension? I don't need that
but I'm just curious if it is possible (neat trick if you can).
--
Mike
Roland Schweitzer wrote:
> Michael,
>
> Change
> Dimension time = file.addDimension("time", 4, false, false, false);
> to
> Dimension time = file.addDimension("time", 4, true, false, false);
> and your example work (at least it did for me with a slightly older jar).
>
> as will
> Dimension time = file.addDimension("time", 4);
>
> AND !!!!!!
>
> add a file.close() at the bottom to write the new values to disk!
> create() makes the empty shell close() commits the writes to disk.
>
> Can't fathom why the API allows a dimension to be created that cannot
> be shared, but it does.
> Nor can I exactly fathom what it means for a dimension to be shared or
> not shared, but there it is.
>
> The Unidata gang will set me straight I'm sure.
>
> Roland
>
>
>
>
> Michael Tiller wrote:
>
>> I'm evaluating a couple of different data storage schemes but I'm having
>> some difficulty with netCDF. First, let me say that I am much happier
>> with the netCDF Java interface than with the way it is handled in
>> HDF5. The fact that the netCDF stuff is not just 100% Java but also
>> done the
>> way a Java interface would normally done has made getting started
>> very easy.
>>
>> However, I do have some problems. I looked in the User's guide and
>> tried putting together some example code based on what is found in
>> Appendix A and I've run into several problems. First let me list my
>> questions and comments and I'll include my sample code (written as a
>> JUnit TestCase) at the end:
>>
>> 1. FYI, I'm using netCDF 2.2.12.
>> 2. The example code in the user's guide seems "out of date". Some of
>> the constructs (use of default constructor for
>> NetcdfFileWriteable, use of Class object arguments in addVariable)
>> are now deprecated in the library.
>> 3. Is there a "bug tracker" for netCDF? Just sending stuff to a
>> mailing list seems like a recipe for falling through the cracks.
>> 4. I get an error when trying to use the NetcdFileWriteable(String
>> file) constructor (it says "Not a netCDF file" or something like
>> that). I added the fill argument and now things work?!?
>> 5. I'm trying to simple record some time series data. So I created a
>> dimension for "time" (i.e. a 1D dataset). The idea (in the code
>> below) is that "h" should be a function of "time". Am I doing
>> that write? It doesn't seem like anything in that code
>> distinguishes "time" as the independent variable!?!
>> 6. The ArrayDouble.D1 "helper" class seems like it could do much
>> more. It has special scalar get and set methods, but what about
>> having "public double[] get()" and "public void set(double [] v)"
>> methods!?! It would make it much easier to initialize the data.
>> 7. I get messages about not being able to load Nexrad and Grib
>> service providers. What are those about? Do I need those? If
>> not, can I shut those warnings off?
>> 8. The example code mentions a class called "ArrayAbstract" which
>> would appear to be handy but I couldn't find it in the jar file.
>> 9. The *main problem* I'm having right now is that I get an error
>> during "file.create()". I get an "IllegalStateException" with the
>> message "unknown Dimension == time = 4; // (has coord.var)". Any
>> ideas?
>>
>> Overall, I'm pretty happy with the design of the system, what can be
>> expressed and the tie in with NcML (which I assume is still ongoing). I
>> just wish I could get my sample code to work. :-)
>>
>> Any help would be very much appreciated. Here is the sample code....
>>
>> import java.io.IOException;
>>
>> import junit.framework.TestCase;
>> import ucar.ma2.ArrayDouble;
>> import ucar.ma2.DataType;
>> import ucar.ma2.InvalidRangeException;
>> import ucar.nc2.Dimension;
>> import ucar.nc2.NetcdfFileWriteable;
>>
>> public class TestNetCDF extends TestCase {
>> public void testCreateData() {
>> NetcdfFileWriteable file = null;
>> file = new NetcdfFileWriteable("./example.nc", true);
>> Dimension time = file.addDimension("time", 4, false,
>> false, false);
>> Dimension dims[] = {time};
>> /* Add time */
>> file.addVariable("time", DataType.DOUBLE, dims);
>> file.addVariableAttribute("time", "quantity", "time");
>> file.addVariableAttribute("time", "units", "s");
>> /* Add a dependent variable */
>> file.addVariable("h", DataType.DOUBLE, dims);
>> file.addVariableAttribute("h", "quantity", "Height");
>> file.addVariableAttribute("h", "units", "m");
>> try {
>> file.create();
>> } catch (IOException e) {
>> e.printStackTrace(System.err);
>> fail("IOException on creation");
>> }
>> double td[] = {1.0, 2.0, 3.0, 4.0};
>> double hd[] = {0.0, 0.1, 0.3, 0.9};
>> ArrayDouble.D1 ta = new ArrayDouble.D1(4);
>> ArrayDouble.D1 ha = new ArrayDouble.D1(4);
>> for(int i=0;i<4;i++) {
>> ta.set(i, td[i]);
>> ha.set(i, hd[i]);
>> }
>> try {
>> file.write("time", ta);
>> } catch (IOException e) {
>> e.printStackTrace(System.err);
>> fail("IOException thrown while writing time");
>> } catch (InvalidRangeException e) {
>> e.printStackTrace(System.err);
>> fail("InvalidRangeException thrown while writing time");
>> }
>> try {
>> file.write("h", ha);
>> } catch (IOException e) {
>> e.printStackTrace(System.err);
>> fail("IOException thrown while writing h");
>> } catch (InvalidRangeException e) {
>> e.printStackTrace(System.err);
>> fail("InvalidRangeException thrown while writing h");
>> }
>> }
>> }
>>
>>
>
begin:vcard fn:Michael Tiller n:Tiller;Michael org:Emmeskay, Inc. adr;dom:;;47119 Five Mile Road;Plymouth;MI;48170 email;internet:mtiller@xxxxxxxxxxxx title:Vice-President Modeling Research and Development tel;work:(734) 635-3450 x-mozilla-html:TRUE url:http://www.emmeskay.com version:2.1 end:vcard
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