[R] random location in polygons sp spsample splancs csr

[Patrick Giraudoux]

Dear all,

I had to place points at random, one in each of larger number of 
polygons (actually in objects of class 'SpatialPolygonsDataFrame' , see 
sp library), and  tried first to do it  using spsample (from sp). 
Surprisingly, every 5-15 trials, the output was a NULL value. The doc 
says that ' this may occur when trying to hit a small and awkwardly 
shaped polygon in a large bounding box with a small number of points', 
but in my case, the shapes were not really awkward, and the bounding box 
just the smallest rectangle including the shape, just the number of 
points was 1 in each polygon.

Thus I tried csr (from splancs) after having extracted the polygon 
coordinates of each shape from the Spatial object, and everything went 
smoothly, with hit success every trial.

Has anybody (anybody will probably be Edzer or/and Roger...) an idea why 
here splancs looks like outperforming spsample ?

Patrick