For the grid defined by x-coordinates, xvals, and
y-coordinates, yvals, and an owin object W, this function
just returns a logical matrix M, whose [i,j] entry is TRUE
if the point(xvals[i], yvals[j]) is inside the observation
window.
criterion for cells being included into
observation window. Either 'touching' or 'centroid'. The
former includes all cells that touch the observation
window, the latter includes all cells whose centroids are
inside the observation window.
Value
matrix of TRUE/FALSE, which elements of the grid are inside
the observation window win