Assign the area to category value

[Houxiang Wang GEO Grad 96]

Hello,

After clumpping (using r.clump) the map, I got many continuous polygons. Now I 
want the area of the polygons to be the category value of the corresponding 
polygons so that I can choose polygons according to their area. I forgot the 
appropriate program to fulfil the task and couldn't find it. Would someone 
please give me a hint about this? 

Many thanks in advance,

Houxiang