Re: [igraph] R igraph: why do get.isomorphism functions use the index 0 in mappings?

[Gábor Csárdi]

Hi,

thanks for your report! It is a bug, it was already fixed in the development version.

Best,

Gabor

On Thu, May 2, 2013 at 6:49 PM, Szabolcs Horvát <address@hidden> wrote:

Hello,

I am quite new to igraph, so please be gentle :-)

I'm using the R interface, but I also looked at the C interface.  If I got it right, in the C interface vertex indices start from 0, while in R they start from 1 (that's good and natural for R).

However, the get.isomorphism functions return zeros in the mappings, e.g.

> g1=graph.edgelist(cbind(c(1,2,3,4),c(2,3,4,1)))

> g2=graph.edgelist(cbind(c(2,4,1,3),c(4,1,3,2)))

> graph.get.isomorphisms.vf2(g1,g2)

[[1]]

[1] 0 2 1 3

[[2]]

[1] 1 3 2 0

[[3]]

[1] 2 0 3 1

[[4]]

[1] 3 1 0 2

This seems inconsistent with the 1-based indexing of R.

Also, some other functions return maps which don't use 0:

> graph.isomorphic.vf2(g1,g2)

$iso

[1] TRUE

$map12

[1] 1 3 2 4

$map21

[1] 1 3 2 4

Is this by design, or is it an oversight?

Szabolcs

_______________________________________________
igraph-help mailing list
address@hidden
https://lists.nongnu.org/mailman/listinfo/igraph-help

--
Gabor Csardi <address@hidden>     MTA KFKI RMKI