[R-sig-Geo] Spatial categories for risk data.

ONKELINX, Thierry Thierry.ONKELINX at inbo.be
Fri Dec 18 11:53:03 CET 2009

Dear Arthur,

I have not seen any responses, therefore I will have a go.

I would start to interpolate the continuous risk score using kriging
(e.g. krige in the gstat package). This will give you a continuous map.
Then you could categorise that map. Kriging requires that you have only
one value per location. In case of overlapping persons you could move
then slightly in a random fashion.

Kriging will not guarantee that the lines are somewhat straight. If you
insist on that, then I would rather use a linear model on the risk score
usin the coordinates as covariates.


ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek
team Biometrie & Kwaliteitszorg
Gaverstraat 4
9500 Geraardsbergen

Research Institute for Nature and Forest
team Biometrics & Quality Assurance
Gaverstraat 4
9500 Geraardsbergen

tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be

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than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-sig-geo-bounces at stat.math.ethz.ch
[mailto:r-sig-geo-bounces at stat.math.ethz.ch] Namens HINTERMEISTER,
ARTHUR W. (Artie)
Verzonden: donderdag 10 december 2009 17:08
Aan: r-sig-geo at stat.math.ethz.ch
Onderwerp: [R-sig-Geo] Spatial categories for risk data.


I currently have a map that looks something like this:


|   x           x    o   x    o     x   |

|  x     x         x       x     a o  a |

|      a       x       o      o    x    |

|  x      x       o      o     o     a  |

|  x  x      x      o       a   o   a  o|

|  x     x     o   x  o   x   a  a    a |

| x   x    o      o     a   a      a    |



x = low risk

o = moderate risk

a = high risk

Each letter represents a person, and the entire map represents a state.
Each person's "risk score" is a continuous numeric value, but I have
categorized it into low, moderate, and high for visual simplicity. What
I'm hoping to do is draw lines that will divide out the categories. The
lines do not have to necessarily be straight, but I would like them to
be simple enough. I figure that I would have to account for any
overlapping or outlying persons. This is my initial idea of how the map
would turn out:


|                  /             /      |

|                 /             /       |

|      x         /     o       /    a   |

|               /             /         |

|              /             /          |

|             /             /           |

|            /             /            |


I have downloaded and installed GRASS and R, but I am not sure what type
of spatial method or analysis to use. Could someone please offer me
advice on how to get started with this project? Thanks so much!


Arthur Hintermeister

ahintermeister at amica.com <mailto:ahintermeister at amica.com> 

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