variogram Compute Spatial Variogram

Description

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

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.

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

References

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

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

See Also

correlogram

Examples

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