GeoDataFrame
A GeoDataFrame is a tabular data structure that contains a GeoSeries.
The most important property of a GeoDataFrame is that it always has one GeoSeries column that holds a special status. This GeoSeries is referred to as the GeoDataFrame’s “geometry”. When a spatial method is applied to a GeoDataFrame (or a spatial attribute like area is called), this commands will always act on the “geometry” column.
The “geometry” column – no matter its name – can be accessed through the geometry attribute (gdf.geometry), and the name of the geometry column can be found by typing gdf.geometry.name.
A GeoDataFrame may also contain other columns with geometrical (shapely) objects, but only one column can be the active geometry at a time. To change which column is the active geometry column, use the GeoDataFrame.set_geometry() method.
An example using the worlds GeoDataFrame:
In [1]: world = geopandas.read_file(geopandas.datasets.get_path('naturalearth_lowres'))
In [2]: world.head()
Out[2]:
pop_est continent name iso_a3 gdp_md_est geometry
0 920938 Oceania Fiji FJI 8374.0 MULTIPOLYGON (((180.00000 -16.06713, 180.00000...
1 53950935 Africa Tanzania TZA 150600.0 POLYGON ((33.90371 -0.95000, 34.07262 -1.05982...
2 603253 Africa W. Sahara ESH 906.5 POLYGON ((-8.66559 27.65643, -8.66512 27.58948...
3 35623680 North America Canada CAN 1674000.0 MULTIPOLYGON (((-122.84000 49.00000, -122.9742...
4 326625791 North America United States of America USA 18560000.0 MULTIPOLYGON (((-122.84000 49.00000, -120.0000...
#Plot countries
In [3]: world.plot();
Currently, the column named “geometry” with country borders is the active geometry column:
In [4]: world.geometry.name
Out[4]: 'geometry'
We can also rename this column to “borders”:
In [5]: world = world.rename(columns={'geometry': 'borders'}).set_geometry('borders')
In [6]: world.geometry.name
Out[6]: 'borders'
Now, we create centroids and make it the geometry:
In [7]: world['centroid_column'] = world.centroid
In [8]: world = world.set_geometry('centroid_column')
In [9]: world.plot();
Note: A GeoDataFrame keeps track of the active column by name, so if you rename the active geometry column, you must also reset the geometry:
gdf = gdf.rename(columns={'old_name': 'new_name'}).set_geometry('new_name')
Note 2: Somewhat confusingly, by default when you use the read_file command, the column containing spatial objects from the file is named “geometry” by default, and will be set as the active geometry column. However, despite using the same term for the name of the column and the name of the special attribute that keeps track of the active column, they are distinct. You can easily shift the active geometry column to a different GeoSeries with the set_geometry() command. Further, gdf.geometry will always return the active geometry column, not the column named geometry. If you wish to call a column named “geometry”, and a different column is the active geometry column, use gdf['geometry'], not gdf.geometry.
Attributes and Methods
Any of the attributes calls or methods described for a GeoSeries will work on a GeoDataFrame – effectively, they are just applied to the “geometry” GeoSeries.
However, GeoDataFrames also have a few extra methods for input and output which are described on the Input and Output page and for geocoding with are described in Geocoding.
Display options
GeoPandas has an options attribute with currently a single configuration option to control:
In [10]: import geopandas
In [11]: geopandas.options
Out[11]:
Options(
display_precision: None [default: None]
The precision (maximum number of decimals) of the coordinates in the
WKT representation in the Series/DataFrame display. By default (None),
it tries to infer and use 3 decimals for projected coordinates and 5
decimals for geographic coordinates.)
The geopandas.options.display_precision option can control the number of decimals to show in the display of coordinates in the geometry column. In the world example of above, the default is to show 5 decimals for geographic coordinates:
In [12]: world['centroid_column'].head()
Out[12]:
0 POINT (163.85316 -17.31631)
1 POINT (34.75299 -6.25773)
2 POINT (-12.13783 24.29117)
3 POINT (-98.14238 61.46908)
4 POINT (-112.59944 45.70563)
Name: centroid_column, dtype: geometry
If you want to change this, for example to see more decimals, you can do:
In [13]: geopandas.options.display_precision = 9
In [14]: world['centroid_column'].head()
Out[14]:
0 POINT (163.853164645 -17.316309426)
1 POINT (34.752989855 -6.257732429)
2 POINT (-12.137831112 24.291172960)
3 POINT (-98.142381372 61.469076145)
4 POINT (-112.599435912 45.705628002)
Name: centroid_column, dtype: geometry
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