[R-sig-Geo] How to establish location of points relative to a line
Roger.Bivand at nhh.no
Fri Oct 10 19:50:56 CEST 2008
On Fri, 10 Oct 2008, Barry Rowlingson wrote:
> 2008/10/10 Bjarke Christensen <Bjarke.Christensen at sydbank.dk>:
>> I have a SpatialLinesDataFrame (A) and a SpatialPointsDataFrame (B). How
>> can I establish which points in B are to the east of a given line in A?
>> The problem is to figure out which persons (whose addresses are geocoded in
>> B) have addresses to the east of a given road (whose coordinates are given
>> in A).
> Is this problem well-defined for a wiggly road? You could be both
> east and west of a particularly curvy road.
> You could take the nearest point of the road to the address location
> and then see if this vector has a positive or negative X component....
Perhaps you could consider completing a polygon with the road on the
"west" edge, for your definition of "west", for example adding the south.
east and north edges of the bounding box of the points to the line (take
care over ring direction!). Then the overlay method would get you there.
> And of course it would be a trivial problem in New York (except for
PS: or Wall St., here today, gone tomorrow?
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