[R-sig-Geo] Minimum bounding circle from cluster of points (Tina Cormier)

[Bacou, Melanie]

Interesting problem, it seems the exact approach is given by Fischer, 
2003 and is implemented in a C++ CGAL package (see 
http://stackoverflow.com/questions/9063453/how-to-compute-the-smallest-bounding-sphere-enclosing-other-bounding-spheres).

I haven't found any binding for R, but there's an implementation in 
PostGIS `ST_MinimumBoundingCircle()` (see 
http://postgis.net/docs/ST_MinimumBoundingCircle.html).

Others might be more up to date.
--Mel.


On 7/9/2016 6:38 AM, Adrian Baddeley wrote:
> Tina Cormier <TinaACormier at gmail.com> wrote:
>
>> I'd like to create a circle around each cluster that is
>> the smallest circle that would encompass all 4 points.
> The circumcircle.
>
> Try the following:
>
> <https://dl.dropboxusercontent.com/u/72421241/test_subplotsToPlots.zip><https://stat.ethz.ch/mailman/listinfo/r-sig-geo>library(spatstat)
>
> circumcircle <- function(x, ...) {   UseMethod("circumcircle") }
>
> circumcircle.owin <- function(x, ...) {
>    d2 <- fardist(x, ..., squared=TRUE)
>    z <- where.min(d2)
>    r <- sqrt(min(d2))
>    w <- disc(centre=z, radius=r)
>    return(w)
> }
>
> circumcircle.ppp <- function(x, ...) {
>    circumcircle(convexhull(x))
> }
>
>
> Adrian Baddeley
>
> 	[[alternative HTML version deleted]]
>
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