Greetings:I am using the PBSMapping package calcVoronoi() routine to calculate ROIs surrounding elements in
an imported ESRI point shape file. Point coords are in decimal lat/long.
here is the gist of the code.....
sites <- read.csv("ThreeCountyPoints.csv")
coordinates(sites) = c("LonDD","LatDD")
xy=coordinates(sites)
events <-
as.EventData(data.frame(EID=1:len,X=xy[,1],Y=xy[,2],projection="LL"))
Vpolys <-calcVoronoi(events) plot.new() plotPolys(Vpolys) # the voronois look good. polyData <- calcArea(Vpolys) # # polyData's Z attribute contains numbers in the magnitude.01 - .0001 # Two questions: 1) What are the units of polyData.Z , and how can I convert them to km**2 ?If I try to convert the units to UTM, as suggested in the PBSMapping user guide, as below,
attr(Vpolys,"zone") <- 9 VpolysUTM <- convUL(Vpolys) I get the error: --> Error in convUL(Vpolys) : Missing or invalid projection attribute.2) Can you suggest a way in which I could clip the Voronois in the polySet using as a clipping polygon the county boundary polygons contained in a polyset (TcPoly), generated from an incoming polygon shapefile (also lat/lon DD):
TriCounty <-read.shape("TriCountyPolyDD.shp")
TcPolys = Map2poly(TriCounty)
# here are the contents of the TriCountyPolyDD shapefile:
# GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",
#
SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]
Please see attached jpg for the 'big picture' Many thanks for any suggestions! Regards, Rick Reeves UCSB / NCEAS -- Rick Reeves Scientific Programmer / Analyst National Center for Ecological Analysis and Synthesis UC Santa Barbara [EMAIL PROTECTED] www.nceas.ucsb.edu 805 892 2533
<<attachment: PbsVoronoiWCty.jpg>>
begin:vcard fn:Rick Reeves n:Reeves;Rick org:UC Santa Barbara;National Center For Ecological Analysis and Synthesis adr:Suite 300;;735 State Street;Santa Barbara;CA;93101;USA email;internet:[EMAIL PROTECTED] title:Rick Reeves, Scientific Programmer/Analyst tel;work:805 892 2533 url:http://www.nceas.ucsb.edu version:2.1 end:vcard
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