def compute_hull(fargs):
'''Compute the convex hull for a set of nodes
Returns a geojson object.
'''
clustidx, nodes = fargs
points = np.array([(x.lon, x.lat) for x in nodes], dtype=int)
try:
hull = topotools.get_concave_hull(points, args.alphacut)
feature = geojson.Feature(
id=clustidx,
geometry=hull,
properties={
'clust': clustidx
}
)
except QhullError:
log.exception("Error in Qhull, returning null for cluster"
" %i with %i nodes" % (clustidx, len(points)))
feature = None
return feature
# keep a list of nodes we orphan
orphans = []
good_nodes = []
for clustidx, nodes in clustered_nodes:
node_list = list(nodes)
points = np.array([(x.lon, x.lat) for x in node_list], dtype=float)
if len(node_list) < 20:
log.info("Cluster has less than 20 nodes, orphaning")
orphans.extend(node_list)
continue
log.info("Cleaning community %i with %i points", clustidx, len(points))
concave_hull = topotools.get_concave_hull(points, args.alphacut)
# So tiny it doesn't even have a hull
if concave_hull is None:
log.info("No concave hull, orphaning judicously")
orphans.extend(node_list)
continue
concave_area = concave_hull.area
log.info("Found concave hull with area %g", concave_area)
convex_hull = topotools.get_convex_hull(points)
convex_area = convex_hull.area
log.info("Found convex hull with area %g", convex_area)
if not convex_area:
log.warning("Community has no area! Discarding all nodes")
orphans.extend(node_list)
