Re: [GRASS-user] average calculation

2009-05-14 Thread Glynn Clements
Seb wrote: > If one were to calculate an average of several rasters, one could simply > do: > > r.mapcalc "ave = (A + B + C) / 3" > > But how can we get around the problem of null values in any of the > rasters, which would propagate it to the result? What is an efficient > way to calculate bo

Re: [GRASS-user] average calculation

2009-05-13 Thread Hamish
Seb wrote: > If one were to calculate an average of several rasters, one > could simply > do: > > r.mapcalc "ave = (A + B + C) / 3" > > But how can we get around the problem of null values in any of the > rasters, which would propagate it to the result? What is an efficient > way to calculate b

[GRASS-user] average calculation

2009-05-13 Thread Seb
Hi, If one were to calculate an average of several rasters, one could simply do: r.mapcalc "ave = (A + B + C) / 3" But how can we get around the problem of null values in any of the rasters, which would propagate it to the result? What is an efficient way to calculate both the numerator and den