Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Due to the current gap in continued funding from the U.S. National Science Foundation (NSF), the NSF Unidata Program Center has temporarily paused most operations. See NSF Unidata Pause in Most Operations for details.
Hi Don, Thanks for your quick reply. I switched to 2.2.17 and the problem is still there. The values of temperature from ncdump include (file is large!): 32767, 32767, 32767, 32767, 32767, 32767, 32767, 32767, 32767, -20974, -20974, -20979, -20985, 32767, 32767, 32767, 32767, -21054, -21072, -21083, -21093, -21101, -21108, -21112, -21115, 32767, 32767, 32767, 32767 represents missing data (metadata has :_FillValue = 32767;) and, for example, -21072 represents (-21072 * 0.001 + 20=) -1.072 degrees C, which is within the valid range. According to the file metadata, the convention is COARDS. Also, as I said in my original post, ncBrowse displays the data without any problems. Thanks again, Jon On 19/10/06, Don Murray <dmurray@xxxxxxxxxxxxxxxx> wrote:
Hi Jon- I suspect the problem is with the valid_max and valid_min attributes. The library will return NaN if the values are outside the range of the min/max. If the type of the attribute is the same as the variable, they are compared before scale and offset. If they are different they are compared after scaling and offset. I recently found a bug with this that was fixed in the 2.2.17 pre-release, but I'm not sure if that is why you are seeing what you are seeing. What are the values for temperature in ncdump? Don ************************************************************* Don Murray UCAR Unidata Program dmurray@xxxxxxxxxxxxxxxx P.O. Box 3000 (303) 497-8628 Boulder, CO 80307 http://www.unidata.ucar.edu/staff/donm ************************************************************* Jon Blower wrote: > Dear all, > > I'm having some problems reading data from a particular NetCDF file. > The code i'm using is: > > NetcdfDataset nc > NetcdfDataset.openDataset("C:\\data\\OA_20060830.nc", true, null); > GridDataset gd = new GridDataset(nc); > GeoGrid gg = gd.findGridByName("temperature"); > Array arr = gg.readYXData(0, 0); > IndexIterator it = arr.getIndexIteratorFast(); > while (it.hasNext()) { > double val = it.getDoubleNext(); > System.out.println("" + val); > } > nc.close(); > > I just get a load of NaNs, even though I know that there are valid > data in the file (ncBrowse displays the data perfectly). The only > unusual thing about the data is that the data are stored as short > integers, with an offset and scale factor: > > short temperature(time, depth, latitude, longitude); > :long_name = "Temperature"; > :missing_value = 32767; // short > :_FillValue = 32767; // short > :units = "degree_Celsius"; > :valid_min = -3; // short > :valid_max = 40; // short > :add_offset = 20.0; // double > :scale_factor = 0.0010; // double > :comment = "Temperature estimate (by objective analysis)"; > > I understood that the NetcdfDataset class automatically dealt with > offsets and scale factors in "enhanced" mode, which is what I am > using (or trying to use). Hence I was expecting to "see" the data as > an array of doubles. The same happens if I use getFloatNext() or > getShortNext(). > > Can anyone see what I'm doing wrong?
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