Coordinate¶

Coordinate variables define the labeled dimensions of a dataset. They hold all data in memory and support append, prepend, and truncate operations.

Class Hierarchy¶

Variable (base)
  └── CoordinateView (sliced view, read-only)
        └── Coordinate (full coordinate, writable)

Coordinate — the full coordinate with append/prepend/truncate, returned by ds['coord_name'] or creation methods
CoordinateView — a sliced subset, returned by indexing a coordinate

Usage¶

with cfdb.open_dataset(file_path) as ds:
    lat = ds['latitude']
    print(lat.data)        # full array (in memory)
    print(lat.shape)       # (200,)
    print(lat.chunk_shape) # (20,)

Properties¶

Property	Type	Description
`name`	str	Variable name
`data`	np.ndarray	Full coordinate data (always in memory)
`values`	np.ndarray	Alias for `data`
`shape`	tuple	Shape of the coordinate
`chunk_shape`	tuple	Chunk shape
`dtype`	DataType	cfdb data type
`coord_names`	tuple of str	`(name,)` — the coordinate's own name
`ndims`	int	Always 1
`attrs`	Attributes	Variable attributes
`axis`	Axis or None	Physical axis (x, y, z, t, xy)
`step`	number or None	Regular spacing step
`origin`	int	Starting position in global index space
`auto_increment`	bool or None	Whether auto-increment is enabled
`units`	str or None	Physical units
`writable`	bool	Whether the dataset is writable
`loc`	LocationIndexer	Location-based indexer

Methods¶

append(data)¶

Append data to the end of the coordinate. Data must maintain uniqueness and ascending order.

lat.append(np.array([20.0, 20.1], dtype='float32'))

prepend(data)¶

Prepend data to the beginning of the coordinate.

lat.prepend(np.array([-0.2, -0.1], dtype='float32'))

truncate(start=None, stop=None)¶

Truncate the coordinate to keep only values in [start, stop] (inclusive). Accepts coordinate values (e.g., datetimes, floats, or strings for datetime coordinates). None means "from the beginning" / "to the end". Deletes orphaned chunks for both the coordinate and all associated data variables.

# Keep only February 2023
ds['time'].truncate(start='2023-02-01', stop='2023-02-28')

# Remove everything before a latitude
ds['latitude'].truncate(start=-45.0)

iter_chunks(include_data=False, decoded=True)¶

Iterate through chunks. If include_data=False (default), yields tuples of slices. If include_data=True, yields (slices, data) tuples.

Note

Coordinates use the base Variable.iter_chunks signature. Data variables have a different, unified iter_chunks(chunk_shape=None) signature — see DataVariable.

rechunker()¶

Return a Rechunker for this variable.

load()¶

For EDataset: pre-fetch chunks from S3. No-op for local datasets.

update_step(step)¶

Update the step value. Only on writable datasets.

update_axis(axis)¶

Update the axis value. Only on writable datasets.

update_units(units)¶

Update the units value. Only on writable datasets.

get_chunk(sel=None, missing_none=False)¶

Get data from one chunk.

items(decoded=True)¶

Iterate through all individual index positions yielding (index, value) tuples.