On Fri, Nov 15, 2013 at 4:08 PM, Glynn Clements <[email protected]> wrote: ... > The way that weights are used depends upon the specific aggregate > (method) being used. > > However, most of the aggregates have the property that multiplying all > of the weights by the same factor won't change the final result (an > exception is method=count). > > Also, most (if not all) of them have the properties that an integer > weight of N is equivalent to N occurrences of the cell value, and > having all weights equal to one produces the same result as when > weights are not used. > > When weights are used, the calculation for method=average is: > > sum(w[i]*x[i]) / sum(w[i]) > > In the case where all weights are zero, this will end up with both the > numerator and denominator to zero, which produces a null result.
I have taken liberty to merge this into the manual in r58242. TODO: add example... Markus _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
