This isn't the easiest of starting points for a mask, but it can be 
done by using `r.clump'. This will create three data clumps (one 
consisting of the original 1's, the other two of the 0's inside and
the 0's outside). Then you can run `r.mask' to decide which of these
clumps you want to use as a mask...

\_\_\_--\_----\_------\_-------------------- P. Martijn van Leusen --------- 
 \_   \_ \_\_\_\_      \_        Dept of Pre- and Protohistoric Archaeology
  \_\_\_  \_ \_ \_      \_        University of Amsterdam, The Netherlands
   \_      \_    \_ \_\_ \_               martijn@scanner.frw.uva.nl
    \_------\_----\_--\_--\_\_\_\_--------------------------------------
> I've had a few responses but my question wasn't clear, so....
> if I have a raster map that looks like
> 
>                           0000000000
>                           0011111100
>                           0010000100
>                           0010000100
>                           0010000100
>                           0010000100
>                           0011111100
>                           0000000000
> 
> how do I get it to look like 
> 
> 
>                           0000000000
>                           0011111100
>                           0011111100
>                           0011111100
>                           0011111100
>                           0011111100
>                           0011111100
>                           0000000000
> 
> so that I can use it as a MASK?
> 
> -------------------------------------------------------------------------------
> Jeffrey Copeland                      | We're wanted men,
> Colorado State University             | We'll strike again,
> Atmospheric Science                   | But first let's have a beer!
> 303-491-8502                          |
> copeland@homebrew.atmos.colostate.edu | J.Buffet, Great Filling Station Holdup
> -------------------------------------------------------------------------------

