[GRASS-user] Point data to region/area

[H.S.Rai]

I wish to convert point data (say with attribute 'A' having value
between 0 - 100), in to thematic map, showing area divided into four
region as:

Region I  : Value of A between 0-25
Region II : Value of A between 25-50
Region III: Value of A between 50-75
Region IV: Value of A between 75-100

What command or sequence of command I need to use. Any pointer to
document / tutorial will be appreciated.

-- 
H.S.Rai