pygmt.grdfilter: Add parameters filter_type/filter_width and more to set the filter

seisman · seisman · commit 19601b9e1573 · 2026-02-09T15:55:20.000+08:00
diff --git a/pygmt/src/grdfilter.py b/pygmt/src/grdfilter.py
@@ -9,16 +9,126 @@
 from pygmt._typing import PathLike
 from pygmt.alias import Alias, AliasSystem
 from pygmt.clib import Session
+from pygmt.exceptions import GMTParameterError, GMTValueError
 from pygmt.helpers import build_arg_list, fmt_docstring, use_alias
 
 __doctest_skip__ = ["grdfilter"]
 
 
+def _alias_option_F(  # noqa: N802
+    filter_type=None,
+    filter_width=None,
+    hist_bin_width=None,
+    highpass=None,
+    median_quantile=None,
+    hist_center_bins=None,
+    mode_extreme=None,
+    filter=None,  # noqa: A002
+):
+    """
+    Helper function to create the alias list for the -F option.
+    """
+    if filter is not None:
+        kwdict = {
+            "filter_type": filter_type,
+            "filter_width": filter_width,
+            "hist_bin_width": hist_bin_width,
+            "highpass": highpass,
+            "median_quantile": median_quantile,
+            "hist_center_bins": hist_center_bins,
+            "mode_extreme": mode_extreme,
+        }
+        if any(v is not None and v is not False for v in kwdict.values()):
+            raise GMTParameterError(
+                conflicts_with=("filter", kwdict.keys()),
+                reason="'filter' is specified using the unrecommended GMT command string syntax.",
+            )
+        return Alias(filter, name="filter")  # Deprecated raw GMT string.
+
+    if median_quantile is not None and filter_type != "median":
+        raise GMTValueError(
+            filter_type,
+            description="filter type",
+            reason="'filter_type' must be 'median' when 'median_quantile' is set.",
+        )
+    if hist_bin_width is not None and filter_type != "histogram":
+        raise GMTValueError(
+            filter_type,
+            description="filter type",
+            reason="'filter_type' must be 'histogram' when 'hist_bin_width' is set.",
+        )
+    if hist_center_bins is not None and filter_type != "histogram":
+        raise GMTValueError(
+            filter_type,
+            description="filter type",
+            reason="'filter_type' must be 'histogram' when 'hist_center_bins' is set.",
+        )
+    if mode_extreme is not None and filter_type not in {"mlprob", "histogram"}:
+        raise GMTValueError(
+            filter_type,
+            description="filter type",
+            reason="'filter_type' must be 'mlprob' or 'histogram' when 'mode_extreme' is set.",
+        )
+
+    return [
+        Alias(
+            filter_type,
+            name="filter_type",
+            mapping={
+                "boxcar": "b",
+                "cosine_arch": "c",
+                "gaussian": "g",
+                "custom": "f",
+                "operator": "o",
+                "median": "m",
+                "mlprob": "p",
+                "histogram": "h",
+                "minall": "l",
+                "minpos": "L",
+                "maxall": "u",
+                "maxneg": "U",
+            },
+        ),
+        Alias(filter_width, name="filter_width", sep="/"),
+        Alias(hist_bin_width, name="hist_bin_width", prefix="/"),
+        Alias(hist_center_bins, name="hist_center_bins", prefix="+c"),
+        Alias(highpass, name="highpass", prefix="+h"),
+        Alias(median_quantile, name="median_quantile", prefix="+q"),
+        Alias(
+            mode_extreme,
+            name="mode_extreme",
+            mapping={"min": "+l", "max": "+u"},
+        ),
+    ]
+
+
 @fmt_docstring
-@use_alias(D="distance", F="filter", f="coltypes")
-def grdfilter(
+@use_alias(D="distance", f="coltypes")
+def grdfilter(  # noqa: PLR0913
     grid: PathLike | xr.DataArray,
     outgrid: PathLike | None = None,
+    filter_type: Literal[
+        "boxcar",
+        "cosine_arch",
+        "gaussian",
+        "custom",
+        "operator",
+        "median",
+        "mlprob",
+        "histogram",
+        "minall",
+        "minpos",
+        "maxall",
+        "maxneg",
+    ]
+    | None = None,
+    filter_width: Sequence[float] | None = None,
+    highpass: bool = False,
+    median_quantile: float | None = None,
+    hist_bin_width: float | None = None,
+    hist_center_bins: bool = False,
+    mode_extreme: Literal["min", "max"] | None = None,
+    filter: str | None = None,  # noqa: A002
     spacing: Sequence[float | str] | None = None,
     nans: Literal["ignore", "replace", "preserve"] | None = None,
     toggle: bool = False,
@@ -58,19 +168,68 @@ def grdfilter(
     ----------
     $grid
     $outgrid
-    filter : str
-        **b**\|\ **c**\|\ **g**\|\ **o**\|\ **m**\|\ **p**\|\ **h**\ *width*\
-        [/*width2*\][*modifiers*].
-        Name of the filter type you wish to apply, followed by the *width*:
-
-        - **b**: Box Car
-        - **c**: Cosine Arch
-        - **g**: Gaussian
-        - **o**: Operator
-        - **m**: Median
-        - **p**: Maximum Likelihood probability
-        - **h**: Histogram
+    filter_type
+      The filter type. Choose among convolution and non-convolution filters.
 
+      Convolution filters are:
+
+      - ``"boxcar"``: All weights are equal.
+      - ``"cosine_arch"``: Weights follow a cosine arch curve.
+      - ``"gaussian"``: Weights are given by the Gaussian function, where filter width
+        is 6 times the conventional Gaussian sigma.
+      - ``"custom"``: Weights are given by the precomputed values in the filter weight
+        grid file *weight*, which must have odd dimensions; also requires ``distance=0``
+        and output spacing must match input spacing or be integer multiples.
+      - ``"operator"``: Weights are given by the precomputed values in the filter weight
+        grid file *weight*, which must have odd dimensions; also requires ``distance=0``
+        and output spacing must match input spacing or be integer multiples. Weights
+        are assumed to sum to zero so no accumulation of weight sums and normalization
+        will be done.
+
+      Non-convolution filters are:
+
+      - ``"median"``: Returns median value. To select another quantile, use the
+        parameter ``median_quantile`` in the 0-1 range [Default is 0.5, i.e., median].
+      - ``"mlprob"``: Maximum likelihood probability (a mode estimator). Return modal
+        value. If more than one mode is found we return their average value. Set
+        ``mode_extreme`` to ``"min"`` or ``"max"`` to return the lowermost or uppermost
+        of the modal values.
+      - ``"histogram"``: Histogram mode (another mode estimator). Return the modal value
+        as the center of the dominant peak in a histogram. Use parameter
+        ``histogram_center_bins`` to center the bins on multiples of bin width [Default
+        has bin edges that are multiples of bin width]. Use parameter
+        ``histogram_bin_width`` to set the bin width. If more than one mode is found we
+        return their average value. Set ``mode_extreme`` to ``"min"`` or ``"max"`` to
+        return the lowermost or uppermost of the modal values.
+
+      - ``"minall"``: Return minimum of all values.
+      - ``"minpos"``: Return minimum of all positive values only.
+      - ``"maxall"``: Return maximum of all values.
+      - ``"maxneg"``: Return maximum of all negative values only.
+    median_quantile
+        Quantile to use when ``filter_type="median"``. Must be a float in the range 0-1.
+        [Default is 0.5 (median)].
+    hist_bin_width
+        Bin width to use when ``filter_type="histogram"``.
+    hist_center_bins
+        Center the histogram bins on multiples of *histogram_bin_width* when
+        ``filter_type="histogram"``. By default, the bins are aligned such that
+        their edges are on multiples of *hist_bin_width*.
+    mode_extreme
+        Choose which extreme to return when ``filter_type="mlprob"`` or
+        ``filter_type="histogram"`` and multiple modes are found. Options are: ``"min"``
+        to return the lowermost mode, or ``"max"`` to return the uppermost mode. By
+        default, the average of all modes is returned.
+    filter
+        Set the filter type.
+
+        .. deprecated:: v0.19.0
+
+            This parameter is deprecated. Use the parameters ``filter_type``,
+            ``filter_width``, ``hist_bin_width``, ``highpass``, ``median_quantile``,
+            ``hist_center_bins``, and ``mode_extreme`` instead. This parameter still
+            accepts raw GMT CLI strings for the ``-F`` option of the ``grdfilter``
+            module for backward compatibility.
     distance : str
         State how the grid (x,y) relates to the filter *width*:
 
@@ -130,7 +289,8 @@ def grdfilter(
     >>> # and return a filtered grid (saved as netCDF file).
     >>> pygmt.grdfilter(
     ...     grid="@earth_relief_30m_g",
-    ...     filter="m600",
+    ...     filter_type="median",
+    ...     filter_width=600,
     ...     distance="4",
     ...     region=[150, 250, 10, 40],
     ...     spacing=0.5,
@@ -140,9 +300,21 @@ def grdfilter(
     >>> # Apply a Gaussian smoothing filter of 600 km to the input DataArray and return
     >>> # a filtered DataArray with the smoothed grid.
     >>> grid = pygmt.datasets.load_earth_relief()
-    >>> smooth_field = pygmt.grdfilter(grid=grid, filter="g600", distance="4")
+    >>> smooth_field = pygmt.grdfilter(
+    ...     grid=grid, filter_type="gaussian", filter_width=600, distance="4"
+    ... )
     """
     aliasdict = AliasSystem(
+        F=_alias_option_F(
+            fliter_type=filter_type,
+            filter_width=filter_width,
+            hist_bin_width=hist_bin_width,
+            highpass=highpass,
+            median_quantile=median_quantile,
+            hist_center_bins=hist_center_bins,
+            mode_extreme=mode_extreme,
+            filter=filter,
+        ),
         I=Alias(spacing, name="spacing", sep="/", size=2),
         N=Alias(
             nans, name="nans", mapping={"ignore": "i", "replace": "r", "preserve": "p"}
diff --git a/pygmt/tests/test_grdfilter.py b/pygmt/tests/test_grdfilter.py
@@ -47,7 +47,12 @@ def test_grdfilter_dataarray_in_dataarray_out(grid, expected_grid):
     Test grdfilter with an input DataArray, and output as DataArray.
     """
     result = grdfilter(
-        grid=grid, filter="g600", distance="4", region=[-53, -49, -20, -17], cores=2
+        grid=grid,
+        filter_type="gaussian",
+        filter_width=600,
+        distance="4",
+        region=[-53, -49, -20, -17],
+        cores=2,
     )
     # check information of the output grid
     assert isinstance(result, xr.DataArray)
@@ -65,7 +70,8 @@ def test_grdfilter_dataarray_in_file_out(grid, expected_grid):
         result = grdfilter(
             grid,
             outgrid=tmpfile.name,
-            filter="g600",
+            filter_type="gaussian",
+            filter_width=600,
             distance="4",
             region=[-53, -49, -20, -17],
         )
