Re: [igraph] Question about the functions induced.subgraph() and clusters()

[Gábor Csárdi]

On Fri, Mar 21, 2014 at 10:37 AM, address@hidden <address@hidden> wrote:

Hi

 

Is the question below out of that the vertice id has been changed in induced.subgraph()?

If I understand this question correctly, then yes. It creates another graph, internal vertex ids change.

 

G.

If I want to generate a subgraph which contains all the vertices and just delete the edges to make the vertices, which were meant to be delete, to be isolate?

 

best

Xueming

 

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address@hidden

 

发件人： address@hidden

发送时间： 2014-03-21 22:00

收件人： igraph-help

主题： Question about the functions induced.subgraph() and clusters()

 

Hi!

 

It is known to us that the maximal weakly connected component of a connected nework is itself. Just like the code below shows that the elements of Siz_wcc never change.

 

        ga <- erdos.renyi.game(1000, 1500, type = "gnm", directed=TRUE);

        Siz_wcc <- rep(0,10) 

         for(i in 1:10)

         {

             wcca <- clusters(ga, mode="weak")

             largest_wcc_va <- which(wcca$membership == which.max(wcca$csize))

             Siz_wcc[i] <- length(largest_wcc_va)     

             ga <- induced.subgraph(ga, largest_wcc_va, impl="copy_and_delete")

         }

>  Siz_wcc

[1] 936 936 936 936 936 936 936 936 936 936

 

Given two networks ga and gb, if network ga is exactly the same with network gb, then the elements in Siz_wcca and Siz_wccb are also expected to be invariant. But Siz_wcca and Siz_wccb decrease to 1 in the end. How could this happen?

 

         gb <- erdos.renyi.game(1000, 1500, type = "gnm", directed=TRUE);

         ga <- gb          

         Siz_wcca <- rep(0,10) 

         Siz_wccb <- rep(0,10) 

         for(i in 1:10)

         {

             wcca <- clusters(ga, mode="weak")

             largest_wcc_va <- which(wcca$membership == which.max(wcca$csize))

             Siz_wcca[i] <- length(largest_wcc_va)     

             gb <- induced.subgraph(gb, largest_wcc_va, impl="copy_and_delete")

 

             wccb <- clusters(gb, mode="weak")

             largest_wcc_vb <- which(wccb$membership == which.max(wccb$csize))

             Siz_wccb[i] <- length(largest_wcc_vb)

             ga <- induced.subgraph(ga, largest_wcc_vb, impl="copy_and_delete")

          }

> Siz_wcca

[1] 933 854 756 615 331   3   1   1   1   1

> Siz_wccb

[1] 933 845 722 521  46   1   1   1   1   1

 

best

Xueming

 

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address@hidden

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