[igraph] vertex sequence Q

[Ragia Ibrahim]

Dear group,
I had a sub graph induced form larger one
the sub-graph is as follows

> V(subg)
Vertex sequence:
[1] 19 21 22 29 43 48 49
> E(subg)
Edge sequence:
            
[1] 21 -> 19
[2] 22 -> 21
[3] 29 -> 19
[4] 43 -> 22
[5] 48 -> 19
[6] 48 -> 21
[7] 48 -> 22
[8] 48 -> 43
[9] 49 -> 22

when using 
get.all.shortest.paths(subg,22)

I got this Error 
 Error in .Call("R_igraph_get_all_shortest_paths", graph, as.igraph.vs(graph,  : 
  At structural_properties.c:992 : cannot get shortest paths, Invalid vertex id

So I used the vertex place in the sequence

get.all.shortest.paths(subg,2)
and I got htis

 $res
$res[[1]]
[1] 2 1

$res[[2]]
[1] 2


$nrgeo
[1] 1 1 0 0 0 0 0

and I tried that too

get.all.shortest.paths(subg,2,1:7,mode="out")
$res
$res[[1]]
[1] 2 1

$res[[2]]
[1] 2


$nrgeo
[1] 1 1 0 0 0 0 0

 is this seems true ?
the value in $res is it the place of node in vertex sequence?
thanks in advance
Ragia