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## [igraph] problem with vertices

 From: Figa Pelosa Subject: [igraph] problem with vertices Date: Thu, 27 Aug 2009 12:17:45 +0000 (GMT)

```hallo,
after deleting a vertex in the graph, the vertex is still there.. how come?

This is what I do:

g is an undirected graph;

1) I delete all edges whose weight is less than a certain threshold:
for i in range(0, g.vcount()):
for j in range(0, g.vcount()):
if i!=j:
if g.es[g.get_eid(i,j)]["weigth"]<threshold:
g.delete_edges(g.get_eid(i,j))

2) then I look for the vertices with degree equal to zero:
for idx, c1 in enumerate(g.vs):
if g.degree(idx, type=ALL, loops=False)==0:
print(idx)
a = g.vs.select(idx)["name"]
print(a)

3) and I have this output:
43
['xxx']
44
['yyy']

4) So I remove those vertices from the graph:
for idx, c1 in enumerate(g.vs):
if g.degree(idx, type=ALL, loops=False)==0:
g.delete_vertices(idx)

5) I increase the threshold by 1 and remove again some edges -like in 1) but
with an higher threshold-

6) I look again for the vertices with degree equal to zero -like in 2)

7) and I get this:
23
['aaa']
43
['yyy']
93
['zzz']

The vertex called "yyy" (that had ID=44) should be deleted, but after deleting
it, a vertex (ID=43) is called "yyy" as well.
Why?

Thanks a lot
FP

```