Compute Spatial Variogram

Compute spatial (semi-)variogram of spatial data or residuals.

Usage

variogram(krig, nint, plotit = TRUE, ...)

Arguments

krig: trend-surface or kriging object with columns x, y, and z
nint: number of bins used
plotit: logical for plotting
...: parameters for the plot

Value

x and y coordinates of the variogram and cnt, the number of pairs averaged per bin.

Side Effects

Plots the variogram if plotit = TRUE

Details

Divides range of data into nint bins, and computes the average squared difference for pairs with separation in each bin. Returns results for bins with 6 or more pairs.

References

Ripley, B. D. (1981) Spatial Statistics. Wiley.

Venables, W. N. and Ripley, B. D. (2002) Modern Applied Statistics with S. Fourth edition. Springer.

Examples

data(topo, package="MASS")
topo.kr <- surf.ls(2, topo)
variogram(topo.kr, 25)