"""
Function to download the Earth seafloor crustal age dataset from the GMT data server,
and load as :class:`xarray.DataArray`.
The grids are available in various resolutions.
"""
from collections.abc import Sequence
from typing import Literal
import xarray as xr
from pygmt.datasets.load_remote_dataset import _load_remote_dataset
__doctest_skip__ = ["load_earth_age"]
[docs]
def load_earth_age(
resolution: Literal[
"01d", "30m", "20m", "15m", "10m", "06m", "05m", "04m", "03m", "02m", "01m"
] = "01d",
region: Sequence[float] | str | None = None,
registration: Literal["gridline", "pixel"] = "gridline",
) -> xr.DataArray:
r"""
Load the Earth seafloor crustal age dataset in various resolutions.
.. figure:: https://www.generic-mapping-tools.org/remote-datasets/_images/GMT_earth_age.jpg
:width: 80 %
:align: center
Earth seafloor crustal age dataset.
This function downloads the dataset from the GMT data server, caches it in a user
data directory (usually ``~/.gmt/server/earth/earth_age/``), and load the dataset as
an :class:`xarray.DataArray`. An internet connection is required the first time
around, but subsequent calls will load the dataset from the local data directory.
The dataset can also be accessed by specifying a file name in any grid processing
function or plotting method, using the following file name format:
**@earth_age**\_\ *res*\_\ *reg*. *res* is the grid resolution; *reg* is the grid
registration type (**p** for pixel registration, **g** for gridline registration).
If *reg* is omitted (e.g., ``@earth_age_01d``), the gridline-registered grid will be
loaded for grid processing functions and the pixel-registered grid will be loaded
for plotting functions. If *res* is also omitted (i.e., ``@earth_age``), GMT
automatically selects a suitable resolution based on the current region and
projection settings.
This dataset comes with a color palette table (CPT) file, ``@earth_age.cpt``. To use
the dataset-specific CPT when plotting the dataset, explicitly set
``cmap="@earth_age.cpt"``, otherwise GMT's default CPT (*turbo*) will be used. If
the dataset is referenced by the file name in a grid plotting method, the
dataset-specific CPT file is used automatically unless another CPT is specified.
Refer to :gmt-datasets:`earth-age.html` for more details about available datasets,
including version information and references.
Parameters
----------
resolution
The grid resolution. The suffix ``d`` and ``m`` stand for arc-degrees and
arc-minutes.
region
The subregion of the grid to load, in the form of a sequence [*xmin*, *xmax*,
*ymin*, *ymax*] or an ISO country code. Required for grids with resolutions
higher than 5 arc-minutes (i.e., ``"05m"``).
registration
Grid registration type. Either ``"pixel"`` for pixel registration or
``"gridline"`` for gridline registration.
Returns
-------
grid
The Earth seafloor crustal age grid. Coordinates are latitude and longitude in
degrees. Age is in millions of years (Myr).
Note
----
The registration and coordinate system type of the returned
:class:`xarray.DataArray` grid can be accessed via the GMT accessors (i.e.,
``grid.gmt.registration`` and ``grid.gmt.gtype`` respectively). However, these
properties may be lost after specific grid operations (such as slicing) and will
need to be manually set before passing the grid to any PyGMT data processing or
plotting functions. Refer to :class:`pygmt.GMTDataArrayAccessor` for detailed
explanations and workarounds.
Examples
--------
>>> from pygmt.datasets import load_earth_age
>>> # Load the default grid (gridline-registered 1 arc-degree grid)
>>> grid = load_earth_age()
>>> # Load the 30 arc-minutes grid with "gridline" registration
>>> grid = load_earth_age(resolution="30m", registration="gridline")
>>> # Load high-resolution (5 arc-minutes) grid for a specific region
>>> grid = load_earth_age(
... resolution="05m",
... region=[120, 160, 30, 60],
... registration="gridline",
... )
"""
grid = _load_remote_dataset(
name="earth_age",
prefix="earth_age",
resolution=resolution,
region=region,
registration=registration,
)
return grid