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.
On 9/3/07, Roger GALLOU (AGO) <roger.gallou@xxxxxx> wrote:
> Hello,
>
> I'm working with Java nc2 library and I wish to read Etopo files (which
> are in NetCDF format) with the methods of the library. I work with
> MatLab R2006b.
> I want to sample the data in Latitude and Longitude, ie, I don't want to
> read all the data but only two samples among 4.
>
> In Java, I manage to read it with loop in latitude and longitude but
> it isn't satisfied by the process time which is more longer than the
> version with mex version.
>
> Do you know a method with Java which is so faster than with mex functions ?
>
Roger,
Did you know that SNCTOOLS can read NetCDF files into Matlab using
NetCDF-Java? All you have to do is edit "nc_method.m" and change
"method=mexnc" to "method=java".
At least on the file I tried, using SNCTOOLS "nc_varget" function
(java) is then faster than using the mex-file based "NetCDF toolkit":
>> tic;a=nc_varget('VS_ele.nc','lon',[0],[2],[2]);toc
Elapsed time is 0.083326 seconds.
>> a
a =
-72.6249
-72.5983
>> tic;nc=netcdf('VS_ele.nc');a=nc{'lon'}(1:2:3);close(nc);toc
Elapsed time is 0.369757 seconds.
>> a
a =
-72.6249
-72.5983
You can explore the "nc_varget_java.m" routine in the SNCTOOLS
"private" directory to see the NetCDF java routines used.
-Rich
--
Dr. Richard P. Signell (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598
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