XploRe Help : SPKRcorrelogram

Keywords - Function groups - @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Library:	spatial
See also:	SPKRsurfls SPKRsurfgls SPKRexpcov SPKRgaucov SPKRsphercov SPKRtrmat SPKRprmat SPKRsemat SPKRvariogram SPKRmultcontours

Quantlet:		SPKRcorrelogram
Description:		computes spatial correlograms of spatial data or residuals. Initially, it divides the range of the data into nint bins, computes the covariance for pairs with separation in each bin, then divides by the variance. It returns results only for bins with 6 or more pairs.

Reference(s):

Venables, W. N., Ripley, B. D. (1999): Modern Applied Statistics with S-Plus, Third Edition, Springer, New York

Link:

Tutorial: Spatial statistics

Usage:	`res = SPKRcorrelogram (krig, nint)`
Input:
	`krig`	list, (of type "trls" or "trgls") calculated by SPKRsurfls or SPKRsurfgls
	`nint`	scalar, number of bins to be used
Output:
	`res`	list, consisting of components xpres, ypres, cntres
	`res.xpres`	n x 1 vector, x coordinates of the correlogram
	`res.ypres`	n x 1 vector, y coordinates of the correlogram
	`res.cntres`	n x 1 vector, number of pairs averaged per bin

Note:

C-Code from Venables, Ripley (1999) forms the basis of this quantlet. Also check this reference for more details.

Example:

; loads the spatial statistics library library("spatial") ; reads a spatial data set topo = read("topo.dat") ; calculates a polynomial regression surface of order 2 myres = SPKRsurfls(2, topo) ; calculates the correlogram, using 25 bins corres = SPKRcorrelogram(myres, 25)

Result:

A list consisting of x and y coordinates of the correlogram
and the number of pairs averaged per bin.

Author: J. Symanzik, 20000725 license MD*Tech