[R-sig-Geo] Variogram estimation without spatial reference

[Tom Gottfried]

Am 12.06.2012 17:29, schrieb Gunnar Oehmichen:
> Dear R-Sig-Geo list,
>
> as part of an applied field-laboratory course, I will try to estimate
> variograms of soil-lipid contents for two meadows differing in use.
>
> Samples were taken in the following scheme:
>
> Code dist X Y Wat mead Pair
> 21 B6-1 0.0 443840 5451412 B B6 6
> 22 B6-1 0.5 443841 5451410 B B6 6
> 23 B6-1 1.0 443843 5451410 B B6 6
> 24 B6-1 2.0 443844 5451411 B B6 6
> 25 B6-1 4.0 443841 5451410 B B6 6
> 26 B6-1 8.0 443848 5451409 B B6 6
> ...
>
> column dist represents the distance [m] to the preceding point.
>
> This scheme was replicated on each meadow 5 times to facilitate
> replicates of each lag (0.5, 1.0, 2.0, 4.0, 8.0). We picked a random
> point (dist = 0.0) sampled, moved a distance of 0.5 m in a random
> direction, sampled and repeated the procedure with increasing distances.
> Allthough lattitude and longitude were recorded (X and Y), I do not
> consider these values to be helpful, since the measurement error of the
> GPS device is ~ 6m, so a much coarser resolution than needed.
>
> Results of the analysis are still missing, so no need to worry about that.
>
> but to the point, do you know of a way to use functions like variogram()
> with this kind of data?

No, but it should be pretty easy to implement a function that calculates 
semivariance between the rows of your data (using diff()). Taking the 
average of semivariances for each value of dist gives you a 
semivariogram. But it gives you not more than 10 point pairs for each 
distance, which is not much.

HTH,
Tom

> Thanks a lot,
>
> Gunnar Oehmichen
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo