Re: [netcdf-java] Reading an OPeNDAP URL using a constraint expression.

• To: netcdf-java@xxxxxxxxxxxxxxxx
• Subject: Re: [netcdf-java] Reading an OPeNDAP URL using a constraint expression.
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Thu, 10 May 2012 11:29:31 -0600

Hi Brian:

You cant open a dataset with a constraint expression in netcdf-Java.

open the dataset without a constraint expression, and constrain the read.

John

On 5/10/2012 11:14 AM, Brian Schlining wrote:

Hi All,

I'm trying to read an opendap url using a contraint expression in
NetCDF-Java. I checked out the thredds source code and built the latest
version (4.3.9-SNAPSHOT). It *sort of* works but I'm confused about reading
data. Here's my example:

% Note I'm testing this in Matlab. so the code may look like pseudo code.
nc = ucar.nc2.dataset.NetcdfDataset.openDataset('
http://geoport.whoi.edu/thredds/dodsC/examples/OS_M1_20081008_TS.nc?PSAL[0:1:100][0:1:0][0:1:0][0:1:0]'
);
vs = nc.getVariables;
psal = vs.get(0)

psal =

    float PSAL(TIME=101, DEPTH=1, LATITUDE=1, LONGITUDE=1);
      :_CoordinateAxes = "TIME DEPTH LATITUDE LONGITUDE ";
      :missing_value = -1.0E34f; // float
      :_FillValue = -1.0E34f; // float
      :long_name = "Hourly sea_water_salinity";
      :units = " ";
      :standard_name = "sea_water_salinity";
      :uncertainty = "0.02";
      :valid_min = "30";
      :valid_max = "36";
      :cell_methods = "time: mean";
      :history = "From m1_ctd0001_20081008_original";


% SO the above code worked as expected and everything looks good.
% However when I read the data like so:
array = psal.read()
psalData = array.copyToNDJavaArray();
size(psalData)

ans =

         9043          11

  ???? I was expecting an array with a size of 101 by 1 as defined in the
contraint expression, but it returns the full 9043 by 11 psal dsdata set.
Is there a different way I'm supposed to read the data when a constraint
expression is used? Any guidance on this would be appreciated.

Cheers

-- B
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Brian Schlining
bschlining@xxxxxxxxx
Monterey Bay Aquarium Research Institute



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  • [netcdf-java] Reading an OPeNDAP URL using a constraint expression.
    • From: Brian Schlining