R help - Nov 2002 - Distance between points and a polygon?

Dear R users,

I know that this could easily be solved within a GIS-package, but 
sometimes it's more convenient to use R. So here's my question anyway...

Does anyone of you know about any R-functions/code that calculates the 
distance between a number points and a polygon or polyline? I have 
looked thru the different libraries that deals with spatial statistics 
but haven't found anything.

Thanks,

Hans Gardfjell
Ume? University, Sweden

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Thanks Rolf,

The necessary function do indeed exists in the spatstat package, but 
rather well hidden I would say.
But after looking thru the bdist.points code I came up with this example:
> library(spatstat)
  #Define a matrix with all the points
> points<-matrix(c(1,3,3,3,6,3),3,2,byrow=T) 
  #Define a matrix with the points the polyline consists
of
> pl<-matrix(c(1,1,4,1,4,4),3,2,byrow=T) 
  #Returns the minimun distance for each point to the
polyline
> apply(distppll(points,cbind(pl[-nrow(pl),],pl[-1,])),1,min)
> [1] 2 1 2
Cheers,

Hans Gardfjell
Ume? University, Sweden



Rolf Turner wrote:
> Look at the spatstat package, available from CRAN.
> 
> The function bdist.points() does ***essentially*** what you want.  It
> assumes that the points are the points of a spatial point pattern,
> and that the polygon is the window though which the pattern is
> observed.  But it would not be at all hard to hack this  function
> into a form that would work in a more general context.
> 
> Hope this helps.
> 
> 				cheers,
> 
> 					Rolf Turner
> 					rolf at math.unb.ca
> 


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