Re: [igraph] Cayley Tree

[Marco]

Dear Gabor,

thank you for the R code.

I will look into it, even if my R skills are *very* low. :)

If I don't come up with a pythonic version of this, I will ask you, if
it is ok with you.

Thank you!

marco

--
restituiremo il riso ai salici



On Wed, Nov 18, 2009 at 11:12 PM, Gábor Csárdi <address@hidden> wrote:
> Yep, but the degree of the root node must be the same as for the other
> nodes. graph.tree() creates graphs, where the degree of the root is
> one less.
>
> It is not too hard to fix this, with something like:
>
> cayley.tree <- function(coord, depth) {
>  if (depth==0) return(graph.empty(1))
>  if (depth==1) return(graph.tree(4, 3, mode="undir"))
>  d <- coord-1
>  n1 <- (d^(depth+1)-1) / (d-1)
>  n2 <- (d^depth -1)/ (d-1)
>  g <- graph.tree(n1, d, mode="undir") %du% graph.tree(n2, d, mode="undir")
>  add.edges(g, c(0, n1))
> }
>
> Best,
> Gabor
>
> On Wed, Nov 18, 2009 at 1:41 PM, Tamas Nepusz <address@hidden> wrote:
>> If I understand it right, a k-Cayley tree is simply a tree where each
>> non-leaf vertex has degree k. The standard tree generation routine in
>> igraph therefore builds a Cayley tree if the number of nodes is set
>> appropriately. (See igraph_tree in C, graph.tree in R, Graph.Tree in
>> Python).
>>
>> --
>> Tamas
>>
>> On Wed, Nov 18, 2009 at 12:29:59AM +0100, Marco wrote:
>>> Hi all,
>>>
>>> any ideas on how to implement efficiently a routine to build a Cayley tree?
>>>
>>> Thanks in advance,
>>>
>>> marco
>>>
>>> --
>>> restituiremo il riso ai salici
>>>
>>>
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>
>
>
> --
> Gabor Csardi <address@hidden>     UNIL DGM
>
>
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