r.stats

[Lars Schylberg]

I guess you can compute your index with r.mapcalc
Something like this should do it:

echo "index = log( float(a)/tan(B) )" | r.mapcalc

Maybe you have to apply a multiply factor to get a meaningful value if
the index is in the range 0 to 1, since the output will be integer
value.  I also assume that you have two raster maps a and B.

Lars

Lars Schylberg                          Email: larss at fmi.kth.se  
Dept. of Geodesy and Photogrammetry 
Royal Institute of Technology (KTH)     Tel.   +46 8 790 86 33   
S-100 44  STOCKHOLM, SWEDEN             Fax.   +46 8 790 66 10