[R-sig-Geo] calculate minimum radial separation

Wesley Roberts wroberts at csir.co.za
Fri May 15 14:43:33 CEST 2009

Dear r-sig-geo,

I would like to calculate the minimum radial separation of a polygon. Basically this involves finding the minimum and maximum distance from the centroid of a polygon to its boundary. I am using it to calculate a roundness index (or something approximating that). Using spstat classes and functionality I have been able to calculate the shortest distance between a centroid and its polygon boundary (bdist.points) but would now like to calculate the maximum distance and have not been able to find a suitable function to do so. Below is an example of what I am trying to do, however bdist.points only returns the shortest distance, how do I calculate the maximum distance? 

> w <- owin(c(10,20), c(10,30), unitname=c("foot","feet"))
> p <- ppp(15,20,window=w)
> bdist.points(p)
[1] 5

Is their a plug-and-play function in one of the spatial R packages to calculate the minimum maximum distance from a centroid to its polygon boundary?

Many thanks for your help,

Wesley Roberts MSc.
Researcher: Earth Observation (Ecosystems)
Natural Resources and the Environment
Tel: +27 (21) 888-2490
Fax: +27 (21) 888-2693

"To know the road ahead, ask those coming back."
- Chinese proverb

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