pygmt.grdclip

pygmt.grdclip(grid, *, outgrid=None, region=None, above=None, below=None, between=None, new=None, verbose=None, **kwargs)[source]

Set values in a grid that meet certain criteria to a new value.

Produce a clipped outgrid or xarray.DataArray version of the input grid file.

The parameters above and below allow for a given value to be set for values above or below a set amount, respectively. This allows for extreme values in a grid, such as points below a certain depth when plotting Earth relief, to all be set to the same value.

Full option list at https://docs.generic-mapping-tools.org/6.5/grdclip.html

Aliases:

  • G = outgrid

  • R = region

  • Sa = above

  • Sb = below

  • Si = between

  • Sr = new

  • V = verbose

Parameters:

  • grid (str or xarray.DataArray) –

    Name of the input grid file or the grid loaded as a xarray.DataArray object.

    For reading a specific grid file format or applying basic data operations, see https://docs.generic-mapping-tools.org/6.5/gmt.html#grd-inout-full for the available modifiers.

  • outgrid (str or None) – Name of the output netCDF grid file. For writing a specific grid file format or applying basic data operations to the output grid, see https://docs.generic-mapping-tools.org/6.5/gmt.html#grd-inout-full for the available modifiers.

  • region (str or list) – xmin/xmax/ymin/ymax[+r][+uunit]. Specify the region of interest.

  • above (str or list) – [high, above]. Set all data[i] > high to above.

  • below (str or list) – [low, below]. Set all data[i] < low to below.

  • between (str or list) – [low, high, between]. Set all data[i] >= low and <= high to between.

  • new (str or list) – [old, new]. Set all data[i] == old to new. This is mostly useful when your data are known to be integer values.

  • verbose (bool or str) –

    Select verbosity level [Default is w], which modulates the messages written to stderr. Choose among 7 levels of verbosity:

    • q - Quiet, not even fatal error messages are produced

    • e - Error messages only

    • w - Warnings [Default]

    • t - Timings (report runtimes for time-intensive algorithms)

    • i - Informational messages (same as verbose=True)

    • c - Compatibility warnings

    • d - Debugging messages

Returns:

ret (xarray.DataArray or None) – Return type depends on whether the outgrid parameter is set:

  • 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]
... )
>>> # Report the minimum and maximum data values
>>> [grid.data.min(), grid.data.max()]
[183.5, 1807.0]
>>> # Create a new grid from an input grid. Set all values below 1,000 to
>>> # 0 and all values above 1,500 to 10,000
>>> new_grid = pygmt.grdclip(grid=grid, below=[1000, 0], above=[1500, 10000])
>>> # Report the minimum and maximum data values
>>> [new_grid.data.min(), new_grid.data.max()]
[0.0, 10000.0]

Examples using pygmt.grdclip

Clipping grid values

Clipping grid values