Hi jimmy/gogurt,
The predecessor graph, returned by predecessor_tree, contains all the nodes from the original graph, and edges representing the predecessor relationships given by the map.
In any case, understand that normally you should not have to create an intermediate graph in order to filter a graph, since you can just use the information you had to begin with to directly build the filter.
In your case, notice that to get the information you need you don't need the predecessor map, just the distance map which always gets returned by shortest_distance.
The logic being: all vertices reached by shortest_distance get a distance attributed which is an integer smaller than the size of the graph, otherwise they get attributed an "impossible" distance which is larger than the size of the graph.
(In your case the vertices of interest have distance of less or equal to 2, but as you already tell shortest_distance to stop at distance 2, any vertex that has a higher distance will still be mapped to the "impossible" distance, so we can just compare the distance to the size of the graph.)
All you have to do is create a new property and assign values to it according to what you find in the distance map:
g = gt.Graph()
v = g.vertex( random.randint( 0, g.num_vertices() ) )
dmap = gt.shortest_distance( g, source=v, max_dist=2 )
mymap = g.new_vertex_property( 'bool' )
for w in g.vertices():
if dmap[w] < g.num_vertices():
mymap[w] = True
Now you can use mymap in GraphView.
I haven't actually ran the code so there might be typos.
Good luck and have fun!
Abraços,
l
e
.~´