Re: [igraph] edge indexing

[Gábor Csárdi]

On Mon, Jun 15, 2015 at 10:47 AM, Elena Tea Russo
<address@hidden> wrote:
>
> Thank you too, Gabor.
>
> I can just guess the problems that a "fixed" indexing in a graph could lead 
> to.
> I suppose neither edges and vertex selectors are then reliable after I modify 
> my graph?

Exactly. These are tied to a given graph, and the "modified" graph is
a different graph. In fact the next version of igraph will give an
error if you want to use a vertex/edge sequence with another graph.

Gabor

>  I'll have to rethink a bit my code, but I luckily can manage my problem 
> throughout an adjacency matrix.
>
> Thanks again!
>
> Et Russo
>
> Il giorno 15/giu/2015, alle ore 15:20, Gábor Csárdi <address@hidden> ha 
> scritto:
>
>> Hi,
>>
>> I understand that reassigning ids is very difficult to work with, it
>> was a decision long time ago, and unfortunately we have to live with
>> it now, and for the foreseeable future.
>>
>> A useful way of thinking about this, especially in R, is that igraph
>> _never_ modifies a graph. It always creates new graphs. So when you
>> say delete.edges(), the old graph is not modified, and a new graph is
>> created based on it.
>>
>> In general, you cannot assume anything about the relationship between
>> the internal ids of the old graph and the new graph.
>>
>> I hope this helps,
>> Gabor
>
>
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