[GRASSLIST:3973] determine if a point falls with an area

[Rengie Chan]

Hi. 

I've been using r.mask than r.mask.points to determine if some points
fall within the particular area (in my case, a census tract). The method
works fine but I now have many points and many census tracts to look at,
is there an easier way to do things better? I've been thinking maybe I
can

r.mapcalc "Results = CensusTract.rast * Points.rast" 

where the category values of CensusTract.rast is set to equal the ID of
the census tract, and the category of all points are set to 1. I was
hoping that Results will contain all the points with their category
values equal to the census tract ID. But instead, what I get is a list
of census tracts where at least one point fall in it.

Can you help? Many thanks in advance.

-Rengie