On Fri, Mar 21, 2014 at 10:57 AM, [email protected] <[email protected]>wrote:
> Thank you > > 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, > then which command could I use? > This is not an induced subgraph. You can use subgraph.edges. > Or is there any command can be used to generate a subgraph without > changing the vertice ids? > No, there isn't and there can't be by definition. You can use symbolic vertex names (i.e. a 'name' vertex attribute) instead of internal ids. Depending on what you do, it might be cumbersome because you'll need convert internal ids to names sometimes. Gabor > > best > Xueming > > ------------------------------ > [email protected] > > *From:* Gábor Csárdi <[email protected]> > *Date:* 2014-03-21 22:17 > *To:* Help for igraph users <[email protected]> > *Subject:* Re: [igraph] Question about the functions induced.subgraph() > and clusters() > Internal vertex ids change if you change the graph. E.g. > > set.seed(42) > ga <- erdos.renyi.game(1000, 1500, type = "gnm", directed=TRUE) > ga > wcca <- clusters(ga, mode="weak") > for (i in 1:10) { > largest_wcc_va <- which(wcca$membership == which.max(wcca$csize)) > ga <- induced.subgraph(ga, largest_wcc_va) > } > ga > > Gabor > > > > On Fri, Mar 21, 2014 at 10:00 AM, [email protected] <[email protected] > > wrote: > >> >> 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 >> >> ------------------------------ >> [email protected] >> >> _______________________________________________ >> igraph-help mailing list >> [email protected] >> https://lists.nongnu.org/mailman/listinfo/igraph-help >> >> > > _______________________________________________ > igraph-help mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/igraph-help > >
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