Weighting by how often something shows up

[Lindsey Buck]

I am trying to weight areas of a twoway scatter by how frequent they show up.
For instance
scatter var1 var2

Say I have many observations that show up at the point (1,1) on my scatter plot, but not that many that are at (0,0). I want to make giant hollow circles but they should be much bigger at (1,1) since there are lots more observations at that point. Can you help?
Thanks!

[Wouter Wakker]

Maybe this example will point you in the right direction.

clear
input y x
0 0
1 1
1 1
1 1
1 1
1 1
2 2
2 2
end

preserve
contract y x
list, noobs
scatter y x [w=_freq], msymbol(Oh)
restore

. list, noobs

  +---------------+
  | y   x   _freq |
  |---------------|
  | 0   0       1 |
  | 1   1       5 |
  | 2   2       2 |
  +---------------+