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Re: [igraph] An elementary question

From: Yiorgos Adamopoulos
Subject: Re: [igraph] An elementary question
Date: Thu, 30 Jun 2011 00:08:34 +0300

On Tue, Jun 28, 2011 at 6:12 PM, Moses Boudourides
<address@hidden> wrote:
> I'm sorry to bother you with such a trivial question but it would save
> me some time searching through manuals if you were able to give me
> directly the answer.

With my 1 month experience on igraph, I do not find your question a trivial one.

> Say I have a graph G and all vertices are associated to a binary
> attribute which takes the values 1 and 0, i.e., for each vertex the
> attribute is either 1 or 0.

Since I am not accustomed to igraph's attribute interface, I
constructed an array containing values of 0 and 1. I am indexing the
array using the vertex id.

> (1) G1 which is what it remains from G if we DELETE ALL LINKS
> connecting vertices with attribute 0 (but of course keeping in G1 all
> vertices of G, although some of them now might turn out to be
> isolated)?

Here is what I did. I constructed an Erdos-Renyi G(n,p) graph. From
this graph I got its adjacency matrix (m) which I copied to two other
matrices (m1 and m0).

I iterated through the vertices of the graph. If the attribute was 0,
then I zeroed the respective line and column in the new adjacency

Some drawbacks in my approach that are seen immediately:

1- Isolated vertices are "lost". They can be restored by either
keeping them in a list, inserting a self-loop or some other hack.

2- It is written in C

3- It does not read a CSV. If the list can recommend a parser that
goes from CSV files to an igraph_t maybe this hack I did can improve.

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