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 SPKRexpcov SPKRgaucov SPKRsphercov SPKRtrmat SPKRprmat SPKRsemat SPKRcorrelogram SPKRvariogram SPKRmultcontours

Quantlet: SPKRsurfgls
Description: fits a trend surface by generalized least squares

Reference(s):

Link:
Usage: res = SPKRsurfgls(np, covmod, xmat, nx, dval, alpha, se {, D})
Input:
np scalar, degree of the polynomial surface, an integer in the range 0..6
covmod integer, type of spatial covariance function: 0 = expcov, 1 = gaucov, 2 = sphercov
xmat n x 3 matrix, locations (x_i, y_i) [columns 1 & 2] and observations z_i [column 3]
nx integer, number of bins used for the table of covariances; increasing nx adds accuracy, but also increases the size of the object
dval scalar, range parameter (for spatial covariance function)
alpha scalar, proportion of nugget effect (for spatial covariance function)
se scalar, standard deviation at distance zero (for spatial covariance function)
D optional scalar, dimension of spheres; default D = 2 (only used for spatial covariance function SPKRsphercov)
Output:
res list, consisting of components x, y, z, np, f, alph, l, r, beta, wz, yy, W, l1f, minx, maxx, covmod and type:
res.x n x 1 vector, same as xmat[,1]
res.y n x 1 vector, same as xmat[,2]
res.z n x 1 vector, same as xmat[,3]
res.np scalar, same as input value np
res.f matrix, internal use only
res.alph matrix, internal use only
res.l matrix, internal use only
res.r matrix, internal use only
res.beta matrix, containing (np + 1)(np + 2) / 2 coefficients
res.wz matrix, internal use only
res.yy matrix, internal use only
res.W matrix, internal use only
res.l1f matrix, internal use only
res.minx 1 x 3 vector, minimum of columns of xmat
res.maxx 1 x 3 vector, maximum of columns of xmat
res.covmod scalar, same as input value covmod
res.type string, "trgls"

Note:

Example:
; loads the spatial statistics library
library("spatial")
; reads a spatial data set
topo = read("topo.dat")
; calculates a trend surface of order 2, using expcov as
; spatial covariance function with dval = 0.7, alph = 0,
; and se = 1
myres = SPKRsurfgls(2, 0, topo, 1000, 0.7, 0, 1)
myres

Result:
A list consisting of input parameters, intermediate
and final results of a trend surface by generalized
least squares. This list will be used in other spatial
statistics quantlets such as SPKRtrmat, SPKRcorrelogram,
or SPKRvariogram.

Contents of myres.l1f
[  1,]        1
[  2,]  0.81105
[  3,]  0.78401
[  4,]  0.83406
[  5,]  0.95137
...
[311,] -0.027897
[312,]  0.04782

Contents of myres.minx
[1,]      0.2        0      690

Contents of myres.maxx
[1,]      6.3      6.2      960

Contents of myres.covmod
[1,]        0

Contents of myres.type
[1,] "trgls"



Author: J. Symanzik, 20000725 license MD*Tech
(C) MD*TECH Method and Data Technologies, 05.02.2006