[R-sig-Geo] point.in.polygon() on massive datasets

[Barry Rowlingson]

Markus Loecher wrote:
> Dear all,
> I have a dataset of about 50 million lat/lon coordinates each of which falls into one of 550 polygons.
> I need to assign their memberships and have used point.in.polygon() for that purpose.
> However, the simple way of looping over the 50 million points clearly takes a looong time; 1 million points took about 3-4 days on a fast Linux server with lots of memory.
> Am I overlooking obvious ways of making this massive computation more efficient ? Would R trees help ?
> Should I try to compile the C code for point.in.polygon() (available from gstat) and run it outside R as a standalone executable ?
> I am already using apply() to mitigate the inefficiency of the for loop in R.
> 
> Any help would be greatly appreciated,
> 

  Have you tried the 'overlay' functions from the sp package? Overlaying 
points on polygons using those checks all the polygons for each point in 
one go, so it may do some spatial tree optimising... You might have to 
do your 50 million points in batches though...

Barry