Changes between Version 33 and Version 34 of udg/ecoms


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Timestamp:
Mar 14, 2013 1:58:21 PM (9 years ago)
Author:
antonio
Comment:

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  • udg/ecoms

    v33 v34  
    3737}}}
    3838= The THREDDS Data Server = #s.thredds
     39{{{#!div style="text-align:justify"
    3940The ''SPECS-EUPORIAS Data Portal'' is based on a password-protected `THREDDS data server` providing metadata and data access to a set of georeferenced atmospheric variables using OPeNDAP and other remote data access protocols. The variables names, units and additional metadata follow the [http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html CF convention]. The variables are spatial grids based on multidimensional arrays of indexed values, following Unidata's ''_Coordinate convention''[[FootNote(http://www.unidata.ucar.edu/software/netcdf-java/reference/CoordinateAttributes.html)]][[FootNote(http://www.unidata.ucar.edu/software/netcdf-java/tutorial/GridDatatype.html)]].
    4041
     
    5152Although the `TDS` provides a web interface to explore and access the datasets (shown in [#s.web.access web access section]), it is strongly recommented the use of `OPeNDAP` (a.k.a. `DODS`) client libraries to remotely access the data from scientific computing environments (`R`, `Matlab`, `Python`, etc.). For instance, the `R` function provided in this tutorial is based on the ''NetCDF Java'' OPeNDAP client[[FootNote(http://www.unidata.ucar.edu/software/netcdf-java/documentation.htm)]], using the `rJava` `R` package (a similar approach is been also made for the `Matlab` implementation). Alternatively, the most recent ''NetCDF library'' versions provide access to `OPeNDAP` datasets (this is the solution for the `Python` implementation). In the following, we show a simple example of data access using the `R` package developed as part of the data portal. In particular the ''System4'' datasets can by directly accessed using the `loadSystem4` function, allowing the retrieval of slices for a particular variable in any of the dataset dimensions (`member`/space/`runtime`/`time`). Note that a more ellaborated worked example using `R` is shown in the [#Appendix.rexample R example section].  Moreover, for a better understanding of the datasets structure, the use of the web interface for the `OPeNDAP`  service is also illustrated [#s.web.access web access section].
    5253
     54}}}
    5355= Accesing the Data Portal via `R` = #s.r.access
    5456