subgraph error

*To*: mathgroup at smc.vnet.net*Subject*: [mg125815] subgraph error*From*: dan jack <dan.spectrix at gmail.com>*Date*: Wed, 4 Apr 2012 04:26:21 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

Hello everyone, I have a graph with 5 vertex: gr=Graph[{1->2,1->3,4->1,5->1,1->1}] so the first vertex has a loop, when I call the subgraph with all the vertex departing from 1: Subgraph[gr, 1 -> _ ] I obtain an error: DeleteDuplicates::list: List expected at position 1 in DeleteDuplicates[Join[1,{1,2},{1,3}]] Moreover if you try copy and paste the code I wrote here, probably you won't see this error, but if you try building this graph step by step one edge at time with EdgeAdd command, then I see the error.... I need to manage subgraphs in this way... Any help?