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## Re: [igraph] finding paths of given length

**From**: |
Gábor Csárdi |

**Subject**: |
Re: [igraph] finding paths of given length |

**Date**: |
Thu, 5 Apr 2012 09:31:05 -0400 |

Sorry for the delay! Answers below.
On Tue, Apr 3, 2012 at 11:16 AM, Sam Steingold <address@hidden> wrote:
>*> * Sam Steingold <fqf-zKKw517/address@hidden> [2012-03-23 14:39:02 -0400]:*
>*>*
>*> given a digraph, how do I find all paths of given length?*
>
>* neighborhood() appears to be useful, except that it returned really a*
>* neighborhood, i.e., the vertexes reachable by <= N steps.*
>* What if I want the vertexes reachable in _EXACTLY_ N steps?*
You mean shortest paths here? If yes, then you can calculate
shortest.paths() from a given starting vertex and see which vertices
are n steps away.
>*> what if all the edges in the path must have the same attribute?*
Then remove the rest of the edges from the graph first. Not
surprisingly this is exactly your next question. :)
>* How do I create a subgraph with edges of a fixes specified attribute?*
Select the edges and supply them to delete.edges. E.g. removing edges
under a weight threshold:
delete.edges( g, E(g)[ weight < 0.5 ] )
G.
[...]