[GRASSLIST:5344] r.neighbors can solve my problem bu it doesn't work!!

Hello all.

So, I'm trying to make a drainage density map. To do this, I need to
calculate the length of stream channels within a given area (500x500m) and
then calculate the ratio beetwen this sum and the area of the cell. I have
this idea of use r.neighbors to sum the values of streams in a raster map
(all streams have value=1, other=0), since in its manual there is a method
of SUM and some others (min,max, etc). The problem starts when I try to run
r.neighbors and it tells me that SUM is not legal. With what command I can
perform this operation?

Thanks thanks thanks.

+-------------------------------------------------+

   Carlos Henrique Grohmann de Carvalho - Guano

     Geologist - MSc Student IGc-USP - Brazil

   Linux User #89721 PGP key: www.keyserver.net

+-------------------------------------------------+