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## Re: [igraph] Circular Reingold Tilford on tree is not planar!?

 From: Tamas Nepusz Subject: Re: [igraph] Circular Reingold Tilford on tree is not planar!? Date: Mon, 27 Jun 2011 17:53:28 +0200 User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110516 Lightning/1.0b2 Thunderbird/3.1.10

```Okay, then try this one (given in graph.formula notation):

a-b:c:d:e, c-f:g:h:i:j:k:l:m:n:o

Of course the root is a.

--
T.

On 06/27/2011 05:45 PM, Gábor Csárdi wrote:
> Actually, the graph that Tamas wrote is not a tree. I am still not
> convinced that you can have a graph for which the non-circular layout
> is planar, and the (properly converted) circular one is not.
>
> Gabor
>
> On Mon, Jun 27, 2011 at 11:08 AM, Robert Belleman <address@hidden> wrote:
>> Hi Gabor, Tamás,
>>
>>
>> So it is not possible to derive a circular planar layout from the
>> RT layout?
>>
>> Because surely it must be possible to construct a planar circular
>> layout for any tree?
>>
>> Do you know an alternative?
>>
>> Thanks,
>> -- Rob
>>
>> Tamás Nepusz wrote:
>>>
>>>> it should be planar, AFAIK. If it is not planar, that means that the
>>>> original non-circular one is not planar
>>>
>>> No, it isn't necesarily planar. A while ago I found a graph for which
>>> the RT layout was planar but the circular RT layout wasn't, and I also
>>> thought it was a bug, but it isn't. Try this graph for instance (given
>>> as an edge list):
>>>
>>> 0-1, 0-2, 0-3, 0-4, 0-5, 0-6, 0-7, 0-8, 0-9, 4-10, 9-10
>>>
>>> When you use vertex 0 as root, the RT layout is planar but the circular
>>> RT layout isn't.
>>>
>>> --
>>> T.
>>>
>>>> , the circular one is just the
>>>> transformation of that. Can you send us (in private if it's big, to
>>>> Tamas and me) an example? I think this is a bug.
>>>>
>>>> Best,
>>>> Gabor
>>>>
>>>> On Fri, Jun 24, 2011 at 9:55 AM, Robert Belleman <address@hidden
>>>>>
>>>>> Hi,
>>>>>
>>>>> I am applying the circular Reingold Tilford layout algorithm on a tree
>>>>> consisting of 23k nodes and the same number of edges. I was expecting
>>>>> this
>>>>> algorithm to produce a planar layout but it doesn't.
>>>>>
>>>>> Can anybody enlighten me?
>>>>>
>>>>> Thanks,
>>>>> -- Rob
>>>>>
>>>>> --
>>>>> Robert Belleman, PhD, Computational Science, Faculty of Science
>>>>> Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam
>>>>> The Netherlands. T: +31 20 525 7272/7463 F: +31 20 525 7490
>>>>> W: http://www.science.uva.nl/~robbel/ E: address@hidden
>>>>>
>>>>> _______________________________________________
>>>>> igraph-help mailing list
>>>>> https://lists.nongnu.org/mailman/listinfo/igraph-help
>>>>
>>>>
>>>>
>>>> --
>>>> KFKI RMKI
>>>>
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