Hi all

I have a script that plots alpha hulls, which I am using to investigate the timing & extent of range size collapses for hundreds of plant species across South Australia.

I'm sure this must be an easy question for most - but I am having trouble generating a shapefile that contains all the remaining triangles for a species, given a particular alpha value. The script below will give me a separate shapefile for every polygon, but I don't fancy piecing these together manually in ArcGIS.

Is there an easy way to join together consecutive polygons so that the last item is the union of them all?

Thanks
Allen

alpha1a<-data.frame(xx, yy)
alpha1b<-rbind(alpha1a,alpha1a[1,])
alpha1c<-Polygon(alpha1b)
alpha1d<-Polygons(list(alpha1c),"1")
alpha1e<-SpatialPolygons(list(alpha1d),1:1)
alpha1_data<-data.frame(cbind(alpha1a))
alpha1_df<-SpatialPolygonsDataFrame(alpha1e,alpha1_data)
writeOGR(alpha1_df,"c:/R/AlphaHulls/Shapefiles",paste(this.sp,"alpha1",i,sep=" "),"ESRI Shapefile")

I can provide more detail on other parts of the script if need be?

Allen McIlwee
NatureLinks Policy Support Officer
Nature Conservation Branch

Department for Environment and Heritage
Richmond Rd, KESWICK
T: 61+ 8+ 8124 4733
F: 61+ 8+ 8463 4818
E: allen.mcilwee@sa.gov.au
M: 0427 255 367
A: GPO Box 1047, Adelaide, SA, 5001 AUSTRALIA

<http://www.environment.sa.gov.au>





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