Buffer, dissolve and explode¶

Functions that buffer, dissolve and/or explodes geometries while fixing geometries.

The functions do the same as the geopandas buffer, dissolve and explode methods, except for the following:

Geometries are made valid after buffer and dissolve.
The buffer resolution defaults to 50 (geopandas’ default is 16).
If ‘by’ is not specified, the index will be labeled 0, 1, …, n - 1 after exploded, instead of 0, 0, …, 0 as it will with the geopandas defaults.
index_parts is set to False, which will be the default in a future version of geopandas.
The buff function returns a GeoDataFrame, the geopandas method returns a GeoSeries.

buff(gdf, distance, resolution=50, copy=True, join_style='round', **buffer_kwargs)[source]¶

Buffers a GeoDataFrame with high resolution and returns a new GeoDataFrame.

Parameters:

gdf (GeoDataFrame | GeoSeries) – the GeoDataFrame that will be buffered, dissolved and exploded.
distance (int | float) – the distance (meters, degrees, depending on the crs) to buffer the geometry by
resolution (int) – The number of segments used to approximate a quarter circle. Here defaults to 50, as opposed to the default 16 in geopandas.
join_style (int | str) – Buffer join style.
copy (bool) – Whether to copy the GeoDataFrame before buffering. Defaults to True.
**buffer_kwargs – additional keyword arguments passed to geopandas’ buffer.

Return type:

GeoDataFrame

Returns:

A buffered GeoDataFrame.

buffdiss(gdf, distance, resolution=50, copy=True, n_jobs=1, join_style='round', **dissolve_kwargs)[source]¶

Buffers and dissolves geometries.

It takes a GeoDataFrame and buffer, fixes, dissolves and fixes geometries. If the ‘by’ parameter is not specified, the index will labeled 0, 1, …, n - 1, instead of 0, 0, …, 0. If ‘by’ is speficied, this will be the index.

Parameters:

gdf (GeoDataFrame) – the GeoDataFrame that will be buffered and dissolved.
distance (int | float) – the distance (meters, degrees, depending on the crs) to buffer the geometry by
resolution (int) – The number of segments used to approximate a quarter circle. Here defaults to 50, as opposed to the default 16 in geopandas.
join_style (int | str) – Buffer join style.
copy (bool) – Whether to copy the GeoDataFrame before buffering. Defaults to True.
n_jobs (int) – Number of threads to use. Defaults to 1.
**dissolve_kwargs – additional keyword arguments passed to geopandas’ dissolve.

Return type:

GeoDataFrame

Returns:

A buffered GeoDataFrame where geometries are dissolved.

Examples:¶

Create some random points.

>>> import sgis as sg
>>> import numpy as np
>>> points = sg.read_parquet_url(
...     "https://media.githubusercontent.com/media/statisticsnorway/ssb-sgis/main/tests/testdata/points_oslo.parquet"
... )[["geometry"]]
>>> points["group"] = np.random.choice([*"abd"], len(points))
>>> points["number"] = np.random.random(size=len(points))
>>> points
                           geometry group    number
0    POINT (263122.700 6651184.900)     a  0.878158
1    POINT (272456.100 6653369.500)     a  0.693311
2    POINT (270082.300 6653032.700)     b  0.323960
3    POINT (259804.800 6650339.700)     a  0.606745
4    POINT (272876.200 6652889.100)     a  0.194360
..                              ...   ...       ...
995  POINT (266801.700 6647844.500)     a  0.814424
996  POINT (261274.000 6653593.400)     b  0.769479
997  POINT (263542.900 6645427.000)     a  0.925991
998  POINT (269226.700 6650628.000)     b  0.431972
999  POINT (264570.300 6644239.500)     d  0.555239

Buffer by 100 meters and dissolve.

>>> sg.buffdiss(points, 100)
                                            geometry group    number
0  MULTIPOLYGON (((256421.833 6649878.117, 256420...     d  0.580157

Dissolve by ‘group’ and get sum of columns.

>>> sg.buffdiss(points, 100, by="group", aggfunc="sum")
                                                geometry      number
group
a      MULTIPOLYGON (((258866.258 6648220.031, 258865...  167.265619
b      MULTIPOLYGON (((258404.858 6647830.931, 258404...  171.939169
d      MULTIPOLYGON (((258180.258 6647935.731, 258179...  156.964300

To get the ‘by’ columns as columns, not index.

>>> sg.buffdiss(points, 100, by="group", as_index=False)
  group                                           geometry    number
0     a  MULTIPOLYGON (((258866.258 6648220.031, 258865...  0.323948
1     b  MULTIPOLYGON (((258404.858 6647830.931, 258404...  0.687635
2     d  MULTIPOLYGON (((258180.258 6647935.731, 258179...  0.580157

buffdissexp(gdf, distance, *, resolution=50, index_parts=False, copy=True, grid_size=None, n_jobs=1, join_style='round', **dissolve_kwargs)[source]¶

Buffers and dissolves overlapping geometries.

It takes a GeoDataFrame and buffer, fixes, dissolves, fixes and explodes geometries. If the ‘by’ parameter is not specified, the index will labeled 0, 1, …, n - 1, instead of 0, 0, …, 0. If ‘by’ is speficied, this will be the index.

Parameters:

gdf (GeoDataFrame) – the GeoDataFrame that will be buffered, dissolved and exploded.
distance (int | float) – the distance (meters, degrees, depending on the crs) to buffer the geometry by
resolution (int) – The number of segments used to approximate a quarter circle. Here defaults to 50, as opposed to the default 16 in geopandas.
index_parts (bool) – If False (default), the index after dissolve is respected. If True, an integer index level is added during explode.
copy (bool) – Whether to copy the GeoDataFrame before buffering. Defaults to True.
grid_size (float | int | None) – Rounding of the coordinates. Defaults to None.
n_jobs (int) – Number of threads to use. Defaults to 1.
join_style (int | str) – Buffer join style.
**dissolve_kwargs – additional keyword arguments passed to geopandas’ dissolve.

Return type:

GeoDataFrame

Returns:

A buffered GeoDataFrame where overlapping geometries are dissolved.

buffdissexp_by_cluster(gdf, distance, *, resolution=50, copy=True, n_jobs=1, join_style='round', **dissolve_kwargs)[source]¶

Buffers and dissolves overlapping geometries.

Works exactly like buffdissexp, but, before dissolving, the geometries are divided into clusters based on overlap (uses the function sgis.get_polygon_clusters). The geometries are then dissolved based on this column (and optionally other columns).

This might be many times faster than a regular buffdissexp, if there are many non-overlapping geometries.

Parameters:

gdf (GeoDataFrame) – the GeoDataFrame that will be buffered, dissolved and exploded.
distance (int | float) – the distance (meters, degrees, depending on the crs) to buffer the geometry by
resolution (int) – The number of segments used to approximate a quarter circle. Here defaults to 50, as opposed to the default 16 in geopandas.
join_style (int | str) – Buffer join style.
copy (bool) – Whether to copy the GeoDataFrame before buffering. Defaults to True.
n_jobs (int) – int = 1,
**dissolve_kwargs – additional keyword arguments passed to geopandas’ dissolve.

Return type:

GeoDataFrame

Returns:

A buffered GeoDataFrame where overlapping geometries are dissolved.

diss(gdf, by=None, aggfunc='first', as_index=True, grid_size=None, n_jobs=1, **dissolve_kwargs)[source]¶

Dissolves geometries.

It takes a GeoDataFrame and dissolves and fixes geometries.

Parameters:

gdf (GeoDataFrame) – the GeoDataFrame that will be dissolved and exploded.
by (str | Sequence[str] | None) – Columns to dissolve by.
aggfunc (str | Callable | dict[str, str | Callable]) – How to aggregate the non-geometry colums not in “by”.
as_index (bool) – Whether the ‘by’ columns should be returned as index. Defaults to True to be consistent with geopandas.
grid_size (float | int | None) – Rounding of the coordinates. Defaults to None.
n_jobs (int) – Number of threads to use. Defaults to 1.
**dissolve_kwargs – additional keyword arguments passed to geopandas’ dissolve.

Return type:

GeoDataFrame

Returns:

A GeoDataFrame with dissolved geometries.

diss_by_cluster(gdf, predicate=None, n_jobs=1, **dissolve_kwargs)[source]¶

Dissolves overlapping geometries through clustering with sjoin and networkx.

Works exactly like dissexp, but, before dissolving, the geometries are divided into clusters based on overlap (uses the function sgis.get_polygon_clusters). The geometries are then dissolved based on this column (and optionally other columns).

This might be many times faster than a regular dissexp, if there are many non-overlapping geometries.

Parameters:

gdf (GeoDataFrame) – the GeoDataFrame that will be dissolved and exploded.
predicate – Spatial predicate to use.
n_jobs (int) – Number of threads to use. Defaults to 1.
**dissolve_kwargs – Keyword arguments passed to geopandas’ dissolve.

Return type:

GeoDataFrame

Returns:

A GeoDataFrame where overlapping geometries are dissolved.

dissexp(gdf, by=None, aggfunc='first', as_index=True, index_parts=False, grid_size=None, n_jobs=1, **dissolve_kwargs)[source]¶

Dissolves overlapping geometries.

It takes a GeoDataFrame and dissolves, fixes and explodes geometries.

Parameters:

gdf (GeoDataFrame) – the GeoDataFrame that will be dissolved and exploded.
by (str | Sequence[str] | None) – Columns to dissolve by.
aggfunc (str | Callable | dict[str, str | Callable]) – How to aggregate the non-geometry colums not in “by”.
as_index (bool) – Whether the ‘by’ columns should be returned as index. Defaults to True to be consistent with geopandas.
index_parts (bool) – If False (default), the index after dissolve is respected. If True, an integer index level is added during explode.
grid_size (float | int | None) – Rounding of the coordinates. Defaults to None.
n_jobs (int) – Number of threads to use. Defaults to 1.
**dissolve_kwargs – additional keyword arguments passed to geopandas’ dissolve.

Return type:

GeoDataFrame

Returns:

A GeoDataFrame where overlapping geometries are dissolved.

dissexp_by_cluster(gdf, predicate='intersects', n_jobs=1, **dissolve_kwargs)[source]¶

Dissolves overlapping geometries through clustering with sjoin and networkx.

This might be many times faster than a regular dissexp, if there are many non-overlapping geometries.

Parameters:

gdf (GeoDataFrame) – the GeoDataFrame that will be dissolved and exploded.
predicate (str | None) – Spatial predicate to use.
n_jobs (int) – Number of threads to use. Defaults to 1.
**dissolve_kwargs – Keyword arguments passed to geopandas’ dissolve.

Return type:

GeoDataFrame

Returns:

A GeoDataFrame where overlapping geometries are dissolved.