

Dear Joe,
Maybe you could use a similar process that Marcelino suggested to me yesterday in order to compute the shortest distance from points to a polyline.
You need to 1)convert your point data to ppp object in spatstat, 2)coerce your polygon data to a psp object in spatstat.
3)nncross between the two.
You'll get "dist" - the nearest neighbour distance between the two patterns and "which" the nearest neighbour index of the second pattern.
Maybe it won't be so straightforward to know which ids of the coerced polyline correspond to each polygon but I am not sure about this point.
Best regards,
Pilar


-----Mensaje original-----
De: r-sig-geo-bounces@stat.math.ethz.ch en nombre de BRWIN338@aol.com
Enviado el: jue 21/05/2009 21:14
Para: r-sig-geo@stat.math.ethz.ch
Asunto: [R-sig-Geo] Finding the county shapefile polygon closest to along-lat position
 
Greetings
I have a large number of long-lat locations dispersed over the  US and need 
 
to identify which US county that each point is located in  (or nearest to). 
  
After reading the past posts  and Roger's book, I have been able to use the 
overlay function  
to  identify the appropriate counties for the set of  locations 
with  long-lats lying within or on a polygon boundary.   However, due to  
longlat precision errors (I am assuming), some of the  points lie  outside 
all of 
my shapefile's county polygon  boundaries.   

Is there an R function similar to "overlay" that I could use to find  which 
 
county polygon is closest to each of my longlat points that do  not lie  
within the shapefile's polygons?  I have spent quite a  bit of time  
searching 
and browsing past list discussions and can seem  to find my  answer.

My apologies if I have missed an obvious  answer.

Joe          


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