[R] spatial analysis

Rainer M Krug r.m.krug at gmail.com
Tue Dec 6 09:24:55 CET 2011

Hash: SHA1

On 06/12/11 03:06, Rolf Turner wrote:
> On 06/12/11 01:44, Marianne.ZEYRINGER at ec.europa.eu wrote:
>> Dear all,
>> I am a PhD student in energy modelling. I am completely stuck
>> with the following problem and would be very grateful for any
>> kind of help. I have cells
> Don't we all?  We're made of them. :-)
> What do you mean by ``I have''?  I.e. be a bit more explicit about 
> the nature of your data.
>> and each cell is assigned a number. I would like to form clusters
>> of cells where the sum of the cell numbers in each cluster must 
>> not exceed 250. One restriction is that only neighbouring cells
> Define "neighbouring".
>> can be formed into clusters. In the end I would like to have a
>> list with all possible cell combinations.
> Do you mean all possible ways in which your ``collection of
> cells'' can be subdivided into such clusters?  My guess is that the
> number of such ways could be extremely large.  (Depending of course
> on how many cells there are in the collection.)
>> Is it possible to do this with R If yes, I would very much
>> appreciate all possible hints how to solve it.
> Install the "fortunes" package.  Then type
> fortune("Yoda")
> But if you want useful help you'll have to make your question much 
> clearer.

Agreed - but as it is a spatial question, you should post it at
r-sig-geo at r-project.org, the list of the special interest group
spatial analysis.

I would also look into e.g. GRASS and SAGA, which might be faster with
these kind of spatial calculations.

In general, if I understand you correctly, you can start with each
cell and then "grow outwards" until you hit your stop criteria (sum <=
250), and then you should have your clusters: one solution per
starting cell (assuming symmetric clusters - if the clusters can be
a-symmetric, many many more).



> cheers,
> Rolf Turner
> ______________________________________________ R-help at r-project.org
> mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do
> read the posting guide http://www.R-project.org/posting-guide.html 
> and provide commented, minimal, self-contained, reproducible code.

- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

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