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## Re: [igraph] how to "simplify" a graph

**From**: |
Gábor Csárdi |

**Subject**: |
Re: [igraph] how to "simplify" a graph |

**Date**: |
Wed, 8 Aug 2012 10:19:14 -0400 |

On Mon, Aug 6, 2012 at 5:12 PM, Sam Steingold <address@hidden> wrote:
>* (no, I am not asking about the simplify function)*
>* I have a directed graph with, say, 100 sources and 100,000 destinations,*
>* and only 5 sources which are also destinations.*
>* I am mostly interested in sources, but the destinations clutter*
>* everything.*
>* I want to "simplify" the graph by dropping all the destinations, but I*
>* want to add a "weighted" link between two sources which have common*
>* destinations.*
>* How do I do that?*
I think what you might need is a bipartite projection. In a bipartite
(or two-mode) graph, you have two kind of vertices, e.g. sources and
destinations. When you create a one-mode projection, you create a
graph where two sources are connected if they have a common neighbor
among the destinations. (Or the other way.)
Check http://igraph.sourceforge.net/doc/R/bipartite.projection.html
The number of common neighbors of the two sources is automatically
added as an edge weight, if you set the multiplicity argument to TRUE
(the default).
G.
>* thanks!*
>* --*
>* Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X *
>* 11.0.11103000*
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>
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--
Gabor Csardi <address@hidden> MTA KFKI RMKI