[R-sig-Geo] Minimum bounding circle from cluster of points

[Bacou, Melanie]

Seems the simplest might be to use the circle that contains your points' 
bounding box (same center as the bbox and with a diameter equal to its 
diagonal?
Spatial circles may be defined as SpatialPolygonsDataFrame using 
sampSurf::spCircle().
https://cran.r-project.org/web/packages/sampSurf/sampSurf.pdf
--Mel.


On 7/8/2016 10:31 AM, Tina Cormier wrote:
> Hi all,
>
> Looking for help aggregating some field data subplots to the plot level
> (data currently in shapefile format). I have clusters of 4 points (4
> subplots = 1 plot). I'd like to create a circle around each cluster that is
> the smallest circle that would encompass all 4 points. Sort of like a
> convex hull, but a circle (convex hull, in this case, would give me a
> triangle because of the layout of the subplots). I am familiar with (and
> use frequently) the typical geo packages in R - with rgdal, sp, raster, and
> maptools being my most frequent flyers. Is there a function I'm missing in
> these (or some other) packages that might be able to help me out? In the
> attribute table, I have a unique ID for each plot/cluster. So for each plot
> ID (in this case, consisting of 4 subplots), I'd like to build a circle
> around all of the subplots.
>
>> str(pts)
> Formal class 'SpatialPointsDataFrame' [package "sp"] with 5 slots
>    ..@ data       :'data.frame': 160 obs. of  12 variables:
>    .. ..$ Plot      : num [1:160] 1 1 1 1 2 2 2 2 3 3 ...
>    .. ..$ Subplot   : num [1:160] 1 2 3 4 1 2 3 4 1 2 ...
>
> I should also mention that it's not always 4 points (subplots), and they
> aren't always covering the same size area on the ground, so buffering by a
> constant distance isn't the answer. I have subset out 3 plots (so 12
> subplots) into a test file here:
> https://dl.dropboxusercontent.com/u/72421241/test_subplotsToPlots.zip
>
> I have R version 3.3.0. I know it's customary to include code for what I've
> tried, buuuut, that would be a blank canvas at this point. Googling hasn't
> really been fruitful for this issue, so I thought you folks might have some
> good ideas!
>
> Thanks,
> Tina
>
> 	[[alternative HTML version deleted]]
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo