Hi,
>eg : I want to set 30% of the raster eigenvalue to 1
raster value or raster eigenvalue?
for the former, in ArcGIS, go to Sptatial Analyst tools / raster
creation / create random raster. This will create a raster with values
between 0 and 1. Then do a reclassification: if data <= 0.3, new value =
1. If data >0.3 new value = 0
Jean