Re: [igraph] extracting vertex attributes from an family of graphs

[Gábor Csárdi]

On Fri, Apr 11, 2014 at 5:02 AM, Bob Pap <address@hidden> wrote:

Thanks, I was not sure the second was faster as there are additional calls in my version. Incidentally, thanks for pointing that get.vertex.attribute(g, attr, id) suffices (instead of get.vertex.attribute(g,attr,V(g)[which(V(g)$name==id)])). However, how does index correctly understand that I am using attribute "name"?  

igraph handles the 'name' attribute specially.

 

How if I wanted to identify the vertex by an another attribute?

You cannot.

Gabor

 

Kindly,

Bob Pap

On 11 April 2014 02:52, Gábor Csárdi <address@hidden> wrote:

Yes, but the second can be written as get.vertex.attribute(g, attr, id), which is a lot more readable and it i also slightly faster.

Gabor

On Thu, Apr 10, 2014 at 5:35 PM, Bob Pap <address@hidden> wrote:

Many thanks dear Gabor. I think the following two should do (equivalent?)

1. function(g,id="identifierXX",attr="betweeness") {

get.vertex.attribute(g,attr)[which(V(g)$name==id)]

}

2. function(g,id="identifierXX",attr="betweeness") {

get.vertex.attribute(g,attr,V(g)[which(V(g)$name==id)])

}

Kindly,

Bob Pap

On 10 April 2014 18:45, Gábor Csárdi <address@hidden> wrote:

On Thu, Apr 10, 2014 at 12:31 PM, Bob Pap <address@hidden> wrote:

Dear all,

Unaware of any method for dealing with multigraphs (in my case a family of graphs "g" indexed by time), I handle these by creating a list, indexed by the time period, say "Mygraphs", where Mygraphs[["2014-01-01"]] returns graph g as it was in 2014-01-01.

I face the need to extract a combination of attributes from the series (in the example below the vertex's "id" and "betweeness", ordered by the index of Mygraphs), I do so for example as follows:

sapply(

Mygraphs,

function(g,id="identifierXX",attr="betweeness") {
get.vertex.attribute(induced.subgraph(g, which(V(g)$name==id)),attr)

}

)

I cannot help to think that the use of induced.subgraph could be obviated by specifying the 2 dimensions (id and attr) at once in the extraction, but I how would I restrict get.vertex.attribute to only return the value for vertex "identifierXX" only?

See the 'index' argument of 'get.vertex.attribute'. 

http://igraph.org/r/doc/attributes.html

Gabor

 

Any guidance would be appreciated.

Kindly,

Bob Pap

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