anisotropy gstat
Dave Depew wrote:
Hi All, I suppose this is a rather simple question...however, I'm managing to get more confused the more I read. I'm doing some OK and UK using the R-gstat package...I have some data that is moderately anisotropic. Reading the gstat literature, it would seem that to specify the appropriate parameters for anisotropic variograms I need the set the angle equal to the direction of maximal data continuity? or maximal range?. The ratio of the minimum to maximum range appears to be straightforward enough, but the first part is confusing me. As an example; data(meuse) e<-variogram(dist~1, loc=~x+y,data=meuse, alpha=c(0,45,90,135)) plot(e)
Dave, try require(gstat) data(meuse) coordinates(meuse) = ~x+y e<-variogram(dist~1, meuse, alpha=c(0,45,90,135)) plot(e, vgm(.08, "Sph", 5000, anis=c(45, .2))) I got there with a bit of trial and error. Clearly, for the 45 degrees most happens beyond 1500 m. Of course this is just for the idea; a variogram model that has some parabolic behaviour at the origin would be prefered.
Looks to me anyways, that the direction of maximum range is 45 deg, and the minRange/maxRange is ~ 1000/1500 = 0.67.
the max correlation direction is 45, the range is, in my model, 5000, the anisotropy ratio 0.2.
Could more experienced gstat users tell me if I'm out to lunch on this one??
You weren't far off. -- Edzer