Compute Spatial Correlograms

Compute spatial correlograms of spatial data or residuals.

Usage

correlogram(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 correlogram, and cnt, the number of pairs averaged per bin.

Side Effects

Plots the correlogram if plotit = TRUE.

Details

Divides range of data into nint bins, and computes the covariance for pairs with separation in each bin, then divides by the variance. 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)
correlogram(topo.kr, 25)
d <- seq(0, 7, 0.1)
lines(d, expcov(d, 0.7))