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

[Tamas Nepusz]

Hi Rob,

The alternative is the radial tree layout, which works by placing nodes on
concentric circles and allocating disjoint spatial segments to different
subtrees in a way that the area of a segment is roughly proportional to the
number of nodes in a subtree. Unfortunately this is not implemented in
igraph yet.

-- 
Tamas

On 06/27/2011 05:08 PM, Robert Belleman wrote:
> Hi Gabor, Tamás,
> 
> Thanks for your answers.
> 
> 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
>>> <mailto:address@hidden>> wrote:
>>>> 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
>>>> <mailto:address@hidden>
>>>>
>>>> _______________________________________________
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>>>
>>>
>>>
>>> --
>>> Gabor Csardi <address@hidden <mailto:address@hidden>> MTA
>>> KFKI RMKI
>>>
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>>
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