XploRe Help : SPKRtrmat

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 SPKRprmat SPKRsemat SPKRcorrelogram SPKRvariogram SPKRmultcontours

Quantlet:		SPKRtrmat
Description:		evaluates a trend surface over a grid

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 = SPKRtrmat(obj, xl, xu, yl, yu, n)`
Input:
	`obj`	list, (of type "trls" or "trgls") calculated by SPKRsurfls or SPKRsurfgls
	`xl`	scalar, lower limit in x-direction of the rectangle for grid
	`xu`	scalar, upper limit in x-direction of the rectangle for grid
	`yl`	scalar, lower limit in y-direction of the rectangle for grid
	`yu`	scalar, upper limit in y-direction of the rectangle for grid
	`n`	scalar, used to create a n x n grid within the rectangle
Output:
	`res`	list, consisting of components z, xl, xu, yl, yu, n and type; for further usage with SPKRmultcontours
	`res.z`	(n+1)^2 x 3 matrix, grid
	`res.xl`	scalar, same as input value xl
	`res.xu`	scalar, same as input value xu
	`res.yl`	scalar, same as input value yl
	`res.yu`	scalar, same as input value yu
	`res.n`	scalar, same as input value n
	`res.type`	string, "trmat"

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 a 30 x 30 grid within [0, 6.5] x [0, 6.5] ; using trend surface myres mygrid = SPKRtrmat(myres, 0, 6.5, 0, 6.5, 30) mygrid

Result:

A grid suitable for display through SPKRmultcontours:

Contents of mygrid.z
[  1,]        0        0   976.33
[  2,]  0.21667        0   965.32
[  3,]  0.43333        0   955.01
[  4,]     0.65        0   945.38
[  5,]  0.86667        0   936.44
...

Contents of mygrid.xl
[1,]        0

Contents of mygrid.xu
[1,]      6.5

Contents of mygrid.yl
[1,]        0

Contents of mygrid.yu
[1,]      6.5

Contents of mygrid.n
[1,]       30

Contents of mygrid.type
[1,] "trmat"

Author: J. Symanzik, 20000725 license MD*Tech