over(x, y, returnList = FALSE, fn = NULL)
xlength(x), or a data.frame with number
of rows equal to length(x). If returnList is FALSE,
a vector with indices of y for each geometry (point, grid
cell centre, polygon or lines) in x. if returnList is
TRUE, a list of length length(x), with list element i
the vector of indices of the geometries in y that correspond
to the $i$-th geometry in x.