cf.CoordinateReference

---

class cf.CoordinateReference(coordinates=None, datum=None, coordinate_conversion=None, source=None, copy=True)

Bases: cfdm.coordinatereference.CoordinateReference

A coordinate reference construct of the CF data model.

A coordinate reference construct relates the coordinate values of the coordinate system to locations in a planetary reference frame.

The domain of a field construct may contain various coordinate systems, each of which is constructed from a subset of the dimension and auxiliary coordinate constructs. For example, the domain of a four-dimensional field construct may contain horizontal (y-x), vertical (z), and temporal (t) coordinate systems. There may be more than one of each of these, if there is more than one coordinate construct applying to a particular spatiotemporal dimension (for example, there could be both latitude-longitude and y-x projection coordinate systems). In general, a coordinate system may be constructed implicitly from any subset of the coordinate constructs, yet a coordinate construct does not need to be explicitly or exclusively associated with any coordinate system.

A coordinate system of the field construct can be explicitly defined by a coordinate reference construct which relates the coordinate values of the coordinate system to locations in a planetary reference frame and consists of the following:

• References to the dimension coordinate and auxiliary coordinate constructs that define the coordinate system to which the coordinate reference construct applies. Note that the coordinate values are not relevant to the coordinate reference construct, only their properties.

• A definition of a datum specifying the zeroes of the dimension and auxiliary coordinate constructs which define the coordinate system. The datum may be implied by the metadata of the referenced dimension and auxiliary coordinate constructs, or explicitly provided.

• A coordinate conversion, which defines a formula for converting coordinate values taken from the dimension or auxiliary coordinate constructs to a different coordinate system. A coordinate reference construct relates the coordinate values of the field to locations in a planetary reference frame.

NetCDF interface

The netCDF grid mapping variable name of a coordinate reference construct may be accessed with the nc_set_variable, nc_get_variable, nc_del_variable and nc_has_variable methods.

Initialisation

Parameters

coordinates: sequence of str, optional

Identify the related dimension and auxiliary coordinate constructs by their construct identifiers.

The coordinates may also be set after initialisation with the set_coordinates and set_coordinate methods.

Parameter example:

coordinates=['dimensioncoordinate2']

Parameter example:

coordinates=('dimensioncoordinate0', 'dimensioncoordinate1')

datum: Datum, optional

Set the datum component of the coordinate reference construct.

The datum may also be set after initialisation with the set_datum method.

coordinate_conversion: CoordinateConversion, optional

Set the coordinate conversion component of the coordinate reference construct.

The coordinate conversion may also be set after initialisation with the set_coordinate_conversion method.

source: optional

Convert source, which can be any type of object, to a CoordinateReference instance.

All other parameters, apart from copy, are ignored and their values are instead inferred from source by assuming that it has the CoordinateReference API. Any parameters that can not be retrieved from source in this way are assumed to have their default value.

Note that if x is also a CoordinateReference instance then cf.CoordinateReference(source=x) is equivalent to x.copy().

copy: bool, optional

If True (the default) then deep copy the input parameters prior to initialisation. By default the parameters are not deep copied.

Inspection

Methods

dump	A full description of the coordinate reference construct.
identity	Return the canonical identity.
identities	Returns all possible identities.

Attributes

construct_type

Return a description of the construct type.

Dictionary-access methods

Methods

get	Return a parameter value of the datum or the coordinate conversion.
__getitem__	Return a parameter value of the datum or the coordinate conversion.

Selection

Methods

match_by_identity

Determine whether or not one of the identities matches.

Coordinates

Methods

del_coordinate	Remove a reference to a coordinate construct.
has_coordinate	Whether a reference to a coordinate construct has been set.
set_coordinate	Set a reference to a coordinate construct.
coordinates	Return all references to coordinate constructs.
clear_coordinates	Remove all references to coordinate constructs.
set_coordinates	Set references to coordinate constructs.

Datum

Methods

del_datum	Remove the datum component.
get_datum	Return the datum component.
set_datum	Set the datum component.

Attributes

datum

Return the datum component.

Coordinate conversion

Methods

del_coordinate_conversion	Remove the coordinate conversion component.
get_coordinate_conversion	Get the coordinate conversion component.
set_coordinate_conversion	Set the coordinate conversion component.

Attributes

coordinate_conversion

Return the coordinate conversion component.

Miscellaneous

Methods

canonical_units	Return the canonical units for a standard CF coordinate conversion term.
change_identifiers	Change the identifiers of a coordinate reference from a mapping.
close	Close all files referenced by coordinate conversion term values.
copy	Return a deep copy.
creation_commands	Returns the commands to create the coordinate reference.
default_value	Return the default value for an unset standard CF coordinate conversion term.
equals	Whether two coordinate reference constructs are the same.
equivalent	True if two coordinate references are logically equal, False otherwise.
get_original_filenames	The names of files containing the original data and metadata.
has_bounds	Returns False since coordinate reference constructs do not have cell bounds.
hasbounds	False.
inspect	Inspect the attributes.
structural_signature	Return the structural signature of a coordinate reference.

NetCDF

Methods

nc_del_variable	Remove the netCDF variable name.
nc_get_variable	Return the netCDF variable name.
nc_has_variable	Whether the netCDF variable name has been set.
nc_set_variable	Set the netCDF variable name.

Aliases

Methods

match

Alias for cf.CoordinateReference.match_by_identity

Groups

Methods

nc_variable_groups	Return the netCDF variable group hierarchy.
nc_set_variable_groups	Set the netCDF variable group hierarchy.
nc_clear_variable_groups	Remove the netCDF variable group hierarchy.

Special

Methods

__deepcopy__	Called by the copy.deepcopy function.
__repr__	Called by the repr built-in function.
__str__	Called by the str built-in function.

Deprecated

Methods

all_identifiers	Deprecated at version 3.0.0.
ancillaries	Deprecated at version 3.0.0.
conversion	Deprecated at version 3.0.0.
name	Return a name.
parameters	Deprecated at version 3.0.0.
set_term	Deprecated at version 3.0.0.