"""
grdsample - Resample a grid onto a new lattice
"""
import xarray as xr
from pygmt.clib import Session
from pygmt.helpers import (
GMTTempFile,
build_arg_string,
fmt_docstring,
kwargs_to_strings,
use_alias,
)
[docs]@fmt_docstring
@use_alias(
G="outgrid",
J="projection",
I="increment",
R="region",
T="translate",
V="verbose",
f="coltypes",
r="registration",
n="interpolation",
x="cores",
)
@kwargs_to_strings(I="sequence", R="sequence")
def grdsample(grid, **kwargs):
r"""
Change the registration, spacing, or nodes in a grid file.
This reads a grid file and interpolates it to create a new grid
file. It can change the registration with ``translate`` or
``registration``, change the grid-spacing or number of nodes with
``increment``, and set a new sub-region using ``region``. A bicubic
[Default], bilinear, B-spline or nearest-neighbor interpolation is set
with ``interpolation``.
When ``region`` is omitted, the output grid will cover the same region as
the input grid. When ``increment`` is omitted, the grid spacing of the
output grid will be the same as the input grid. Either ``registration`` or
``translate`` can be used to change the grid registration. When omitted,
the output grid will have the same registration as the input grid.
{aliases}
Parameters
----------
grid : str or xarray.DataArray
The file name of the input grid or the grid loaded as a DataArray.
outgrid : str or None
The name of the output netCDF file with extension .nc to store the grid
in.
{I}
{R}
translate : bool
Translate between grid and pixel registration; if the input is
grid-registered, the output will be pixel-registered and vice-versa.
interpolation : str
[**b**\|\ **c**\|\ **l**\|\ **n**][**+a**][**+b**\ *BC*][**+c**]
[**+t**\ *threshold*].
Select interpolation mode for grids.
- **b** to use B-spline smoothing.
- **c** to use bicubic interpolation.
- **l** to use bilinear interpolation.
- **n** to use nearest-neighbor value (for example to plot
categorical data).
The following modifiers are supported:
- **+a** to switch off antialiasing (where supported) [default uses
antialiasing].
- **+b** to override boundary conditions used, by appending *g* for
geographic, *p* for periodic, or *n* for natural boundary conditions.
For the latter two you may append **x** or **y** to specify just one
direction, otherwise both are assumed.
- **+c** to clip the interpolated grid to input z-min/z-max
[default may exceed limits].
- **+t** to control how close to nodes with NaNs the interpolation
will go based on *threshold*. A *threshold* of 1.0 requires all
(4 or 16) nodes involved in interpolation to be non-NaN. For example,
0.5 will interpolate about half way from a non-NaN value and 0.1 will
go about 90% of the way [default is 0.5].
registration : str
[**g**\ |\ **p**\ ].
Set registration to **g**\ ridline or **p**\ ixel.
{V}
{f}
{x}
Returns
-------
ret: xarray.DataArray or None
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``)
"""
with GMTTempFile(suffix=".nc") as tmpfile:
with Session() as lib:
file_context = lib.virtualfile_from_data(check_kind="raster", data=grid)
with file_context as infile:
if "G" not in kwargs.keys(): # if outgrid is unset, output to tempfile
kwargs.update({"G": tmpfile.name})
outgrid = kwargs["G"]
arg_str = " ".join([infile, build_arg_string(kwargs)])
lib.call_module("grdsample", arg_str)
if outgrid == tmpfile.name: # if user did not set outgrid, return DataArray
with xr.open_dataarray(outgrid) as dataarray:
result = dataarray.load()
_ = result.gmt # load GMTDataArray accessor information
else:
result = None # if user sets an outgrid, return None
return result