spatial analysis

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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,

Rainer

cheers,

Rolf Turner

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

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

Tel :       +33 - (0)9 53 10 27 44
Cell:       +33 - (0)6 85 62 59 98
Fax :       +33 - (0)9 58 10 27 44

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email:      Rainer at krugs.de

Skype:      RMkrug
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