2008 Unidata NetCDF Workshop for Developers and Data Providers > Introduction to NetCDF-4
11.4 Groups
Groups provide a scope for names and a scalable way to organize data objects.
Example
Organizing data by a named property such as region:
group USA {
group Colorado {
dimensions: time = unlimited, stations = 47;
variables: float temperature(time, stations);
}
group Wyoming{
dimensions: time = unlimited, stations = 61;
variables: float temperature(time, stations);
}
group Alaska {
dimensions: time = unlimited, stations = 53;
variables: float temperature(time, stations);
}
...
dimensions: time = unlimited;
variables: float average_temperature(time);
}
- Like directories in a file system, Groups provide name spaces and
a hierarchy of containers
- A Group is analogous to a netCDF-3 file: it may have variables,
dimensions, attributes, types, and subgroups
- Use of Groups is
optional, with backward compatibility maintained by putting everything
in the top-level unnamed Group.
- Unlike HDF5, netCDF-4 requires
that Groups form a strict hierarchy.
Potential uses for Groups include
- Factoring out common information
- Containers for data within regions, ensembles
- Model metadata
- Organizing a large number of variables
- Providing name spaces for multiple uses of same names for
dimensions, variables, attributes
- Modeling large hierarchies
2008 Unidata NetCDF Workshop for Developers and Data Providers > Introduction to NetCDF-4