[R] Concave hull

[baptiste auguie]

Thanks for the interesting reference to alphahull. It might be a good
starting point for placing e.g. a legend in a plot (I think the usual
techniques for this (gregmisc?) are a bit more brute-force.)


baptiste

2009/11/27 Kjetil Halvorsen <kjetilbrinchmannhalvorsen at gmail.com>:
> There is a package on CRAN implementing such an idea:
> alphahull, phull is other package,
>
> kjetil
>
> On Thu, Nov 26, 2009 at 6:11 PM, baptiste auguie
> <baptiste.auguie at googlemail.com> wrote:
>> 2009/11/26 Ted Harding <Ted.Harding at manchester.ac.uk>:
>>> Raising a rather general question here.
>>>
>>> This is a tantalising discussion, but the notion of "concave hull"
>>> strikes me as extremely ill-defined!
>>>
>>> I'd like to see statement of what it is (generically) supposed to be.
>>
>> I'm curious too, but I can imagine the following definition,
>>
>> Consider a sphere (n-dimensional maybe) that we let come in contact
>> with the scatter of points from outside. The set of points that the
>> sphere can attain may define unambiguously (I think) a concave hull,
>> for a specified sphere radius. The convex hull is obtained in the
>> limit of infinite radius (plane).
>>
>> It's probably not exactly this, but I guess that's the rough idea.
>>
>> Just a thought,
>>
>> baptiste
>>
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>