User's Guide - netCDF Files

## B.4 netCDF Files

Data Explorer supports the importation of data in netCDF format, a data abstraction for self-describing multidimensional Arrays. It represents a simpler data model than that of Data Explorer, one similar to that of the Array Object. Data are accessed in netCDF through an application programming interface (available in C and FORTRAN libraries from the Unidata Program Center--in Boulder, Colorado).

Scalar data on a regular grid can be imported from a standard netCDF file. To import vector data, data on irregular grids, or time series data, additional attributes must be added to the netCDF file. These attributes allow you to specify the data, positions, and connections components of your data set. See B.5 , "netCDF Files: Complex Fields" for more information about these attributes.

### Regular Grids

To import scalar data on a regular grid, specify the netCDF file name as the `name` parameter. By default, all netCDF variables are imported and collected into a Group. To import one or more particular variables, specify their names as the `variable` parameter. The `format` parameter must be "netCDF."

Data Explorer automatically constructs positions and connections for each variable, with an origin of 0.0 and spacings of 1.0 along each dimension.

For data that is logically a vector Field, but whose values are stored in three separate netCDF variables, each component of the vector can be imported separately; the Compute module can then be used to create a single vector Field.

For data that is logically a vector Field, but whose values are stored as an n+1 dimensional regular grid, use the Slice and Compute modules to separate the components of the vector, and then recombine them into a single vector Field.

#### Example of a Regular Grid

The following file describes a 3 × 3 × 3 regular grid at origin 0, 0, 0 with deltas of 1.0 along each axis.

    netCDF volume {
    dimensions:
       nx = 3;
       ny = 3;
       nz = 3;

    variables:
       float field_data(nx, ny, nz);

    data:
       field_data =
            0, 0, 0
            0, 0, 0
            0, 5, 0

            0, 0, 5
            0, 0, 0
            0, 0, 0

            5, 0, 0
            0, 0, 0
            0, 0, 0;
    }

netCDF on completely regular grids can be imported directly by Data Explorer without modifying the netCDF file. See B.4 , "netCDF Files" for more information.

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