stimmenfryslan/stimmen/geojson.py

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2018-09-28 16:28:15 +02:00
from pygeoif.geometry import mapping
from shapely.geometry import shape
def merge_features(geojson, condition, aggregate={}):
"""Merge the geometries using shapely's union for all the geojson's features that
meet the condition, condition get's passed an item of feature. Then aggregate the properties
in the aggregate dict using a function that get as input the list of property values off alle
matched features. Operates inplace."""
indices = [index for index, feature in enumerate(geojson['features']) if condition(feature)]
if len(indices) == 0: # also if there is one index, we
return geojson
properties = {
prop: agg([
properties_[prop]
for index in indices
for properties_ in [geojson['features'][index]['properties']]
if prop in properties_
])
for prop, agg in aggregate.items()
}
properties.update({
key: value
for index in indices
for key, value in geojson['features'][index]['properties'].items()
if key not in aggregate
})
if len(indices) == 1:
geojson['features'][indices[0]]['properties'] = properties
return geojson
union = shape(geojson['features'][indices[0]]['geometry'])
for index in indices[1:]:
union = union.union(shape(geojson['features'][index]['geometry']))
for index in indices[::-1]: # reverse, such that the 'todo' indices willnot change.
del geojson['features'][index]
geojson['features'].append({
'geometry': mapping(union),
'properties': properties
})
return geojson