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Co-authored-by: Martin Fleischmann <martin@martinfleischmann.net> Co-authored-by: Nathan Korinek <nako1890@colorado.edu> Co-authored-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>
117 lines
4.2 KiB
Python
117 lines
4.2 KiB
Python
"""
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Clip Vector Data with GeoPandas
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==================================================================
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Learn how to clip geometries to the boundary of a polygon geometry
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using GeoPandas.
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.. currentmodule:: geopandas
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"""
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###############################################################################
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#
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# The example below shows you how to clip a set of vector geometries
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# to the spatial extent / shape of another vector object. Both sets of geometries
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# must be opened with GeoPandas as GeoDataFrames and be in the same Coordinate
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# Reference System (CRS) for the :func:`clip` function in GeoPandas to work.
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#
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# This example uses GeoPandas example data ``'naturalearth_cities'`` and
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# ``'naturalearth_lowres'``, alongside a custom rectangle geometry made with
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# shapely and then turned into a GeoDataFrame.
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#
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# .. note::
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# The object to be clipped will be clipped to the full extent of the clip
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# object. If there are multiple polygons in clip object, the input data will
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# be clipped to the total boundary of all polygons in clip object.
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###############################################################################
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# Import Packages
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# ---------------
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#
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# To begin, import the needed packages.
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import matplotlib.pyplot as plt
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import geopandas
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from shapely.geometry import Polygon
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###############################################################################
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# Get or Create Example Data
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# --------------------------
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#
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# Below, the example GeoPandas data is imported and opened as a GeoDataFrame.
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# Additionally, a polygon is created with shapely and then converted into a
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# GeoDataFrame with the same CRS as the GeoPandas world dataset.
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capitals = geopandas.read_file(geopandas.datasets.get_path("naturalearth_cities"))
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world = geopandas.read_file(geopandas.datasets.get_path("naturalearth_lowres"))
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# Create a subset of the world data that is just the South American continent
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south_america = world[world["continent"] == "South America"]
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# Create a custom polygon
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polygon = Polygon([(0, 0), (0, 90), (180, 90), (180, 0), (0, 0)])
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poly_gdf = geopandas.GeoDataFrame([1], geometry=[polygon], crs=world.crs)
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###############################################################################
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# Plot the Unclipped Data
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# -----------------------
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fig, (ax1, ax2) = plt.subplots(2, 1, figsize=(12, 8))
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world.plot(ax=ax1)
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poly_gdf.boundary.plot(ax=ax1, color="red")
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south_america.boundary.plot(ax=ax2, color="green")
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capitals.plot(ax=ax2, color="purple")
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ax1.set_title("All Unclipped World Data", fontsize=20)
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ax2.set_title("All Unclipped Capital Data", fontsize=20)
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ax1.set_axis_off()
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ax2.set_axis_off()
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plt.show()
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###############################################################################
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# Clip the Data
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# --------------
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#
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# When you call :func:`clip`, the first object called is the object that will
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# be clipped. The second object called is the clip extent. The returned output
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# will be a new clipped GeoDataframe. All of the attributes for each returned
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# geometry will be retained when you clip.
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#
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# .. note::
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# Recall that the data must be in the same CRS in order to use the
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# :func:`clip` function. If the data are not in the same CRS, be sure to use
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# the GeoPandas :meth:`~GeoDataFrame.to_crs` method to ensure both datasets
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# are in the same CRS.
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###############################################################################
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# Clip the World Data
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# --------------------
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world_clipped = geopandas.clip(world, polygon)
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# Plot the clipped data
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# The plot below shows the results of the clip function applied to the world
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# sphinx_gallery_thumbnail_number = 2
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fig, ax = plt.subplots(figsize=(12, 8))
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world_clipped.plot(ax=ax, color="purple")
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world.boundary.plot(ax=ax)
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poly_gdf.boundary.plot(ax=ax, color="red")
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ax.set_title("World Clipped", fontsize=20)
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ax.set_axis_off()
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plt.show()
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###############################################################################
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# Clip the Capitals Data
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# ----------------------
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capitals_clipped = geopandas.clip(capitals, south_america)
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# Plot the clipped data
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# The plot below shows the results of the clip function applied to the capital cities
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fig, ax = plt.subplots(figsize=(12, 8))
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capitals_clipped.plot(ax=ax, color="purple")
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south_america.boundary.plot(ax=ax, color="green")
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ax.set_title("Capitals Clipped", fontsize=20)
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ax.set_axis_off()
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plt.show()
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