"""
grdcut - Extract subregion from a grid.
"""
import xarray as xr
from pygmt.clib import Session
from pygmt.helpers import (
GMTTempFile,
build_arg_list,
fmt_docstring,
kwargs_to_strings,
use_alias,
)
from pygmt.io import load_dataarray
__doctest_skip__ = ["grdcut"]
[docs]
@fmt_docstring
@use_alias(
G="outgrid",
R="region",
J="projection",
N="extend",
S="circ_subregion",
V="verbose",
Z="z_subregion",
f="coltypes",
)
@kwargs_to_strings(R="sequence")
def grdcut(grid, **kwargs) -> xr.DataArray | None:
r"""
Extract subregion from a grid.
Produce a new ``outgrid`` file which is a subregion of ``grid``. The
subregion is specified with ``region``; the specified range must not exceed
the range of ``grid`` (but see ``extend``). If in doubt, run
:func:`pygmt.grdinfo` to check range. Alternatively, define the subregion
indirectly via a range check on the node values or via distances from a
given point. Finally, you can give ``projection`` for oblique projections
to determine the corresponding rectangular ``region`` that will give a grid
that fully covers the oblique domain.
Full option list at :gmt-docs:`grdcut.html`
{aliases}
Parameters
----------
{grid}
{outgrid}
{projection}
{region}
extend : bool or float
Allow grid to be extended if new ``region`` exceeds existing
boundaries. Give a value to initialize nodes outside current region.
circ_subregion : str
*lon/lat/radius*\[\ *unit*\][**+n**].
Specify an origin (*lon* and *lat*) and *radius*; append a distance
*unit* and we determine the corresponding rectangular region so that
all grid nodes on or inside the circle are contained in the subset.
If **+n** is appended we set all nodes outside the circle to NaN.
z_subregion : str
[*min/max*\][**+n**\|\ **N**\|\ **r**].
Determine a new rectangular region so that all nodes outside this
region are also outside the given z-range [-inf/+inf]. To indicate no
limit on *min* or *max* only, specify a hyphen (-). Normally, any NaNs
encountered are simply skipped and not considered in the
range-decision. Append **+n** to consider a NaN to be outside the given
z-range. This means the new subset will be NaN-free. Alternatively,
append **+r** to consider NaNs to be within the data range. In this
case we stop shrinking the boundaries once a NaN is found [Default
simply skips NaNs when making the range decision]. Finally, if your
core subset grid is surrounded by rows and/or columns that are all
NaNs, append **+N** to strip off such columns before (optionally)
considering the range of the core subset for further reduction of the
area.
{verbose}
{coltypes}
Returns
-------
ret
Return type depends on whether the ``outgrid`` parameter is set:
- :class:`xarray.DataArray` if ``outgrid`` is not set
- None if ``outgrid`` is set (grid output will be stored in file set by
``outgrid``)
Example
-------
>>> import pygmt
>>> # Load a grid of @earth_relief_30m data, with a longitude range of
>>> # 10° E to 30° E, and a latitude range of 15° N to 25° N
>>> grid = pygmt.datasets.load_earth_relief(
... resolution="30m", region=[10, 30, 15, 25]
... )
>>> # Create a new grid from an input grid, with a longitude range of
>>> # 12° E to 15° E and a latitude range of 21° N to 24° N
>>> new_grid = pygmt.grdcut(grid=grid, region=[12, 15, 21, 24])
"""
with GMTTempFile(suffix=".nc") as tmpfile:
with Session() as lib:
with lib.virtualfile_in(check_kind="raster", data=grid) as vingrd:
if (outgrid := kwargs.get("G")) is None:
kwargs["G"] = outgrid = tmpfile.name # output to tmpfile
lib.call_module(
module="grdcut", args=build_arg_list(kwargs, infile=vingrd)
)
return load_dataarray(outgrid) if outgrid == tmpfile.name else None