[pstricks] cnodes and boxes

[Francisco A. S. Grossi]

I have some nodes in a XY plane (showing a two-dimension sample space) and 
would like to mark certain events. I was able to it with NCBOX when all the 
relevant points are aligned. I would like to mark some points but they would 
form a triangle; I could not find a way to do it unless I specify the actual 
coordinates instead of refering to the cnodes names (I used PSPOLYGON with 
the XY coordinates). Is there an easier way, something like NCBOX?

Francisco