1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
|
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Library General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Library General Public License for more details.
#
# You should have received A copy of the GNU Library General
# Public License along with this library; if not, write to the
# Free Foundation, Inc., 59 Temple Place, Suite 330, Boston,
# MA 02111-1307 USA
# Copyrights (C)
# for this R-port:
# 1999 - 2008, Diethelm Wuertz, Rmetrics Foundation, GPL
# Diethelm Wuertz <wuertz@itp.phys.ethz.ch>
# www.rmetrics.org
# for the code accessed (or partly included) from other R-ports:
# see R's copyright and license files
# for the code accessed (or partly included) from contributed R-ports
# and other sources
# see Rmetrics's copyright file
################################################################################
# FUNCTION: BIVARIATE GRIDDED INTERPOLATION:
# krigeInterp Kriges irregularly distributed data points
################################################################################
krigeInterp <-
function(x, y = NULL, z = NULL, gridPoints = 21,
xo = seq(min(x), max(x), length = gridPoints),
yo = seq(min(y), max(y), length = gridPoints), extrap = FALSE,
polDegree = 6)
{
# A function implemented by Diethelm Wuertz
# Description:
# Kriges Irregularly Distributed Data Points
# Arguments:
# x, y, z - either three numeric vectors of equal length or if
# y and z are NULL, a list with entries x, y, a, or named
# data.frame with x in the first, y in the second, and z in
# the third column.
# gridPoints - number of grid points in x and y direction.
# xo, yo, a sequence of data points spanning the grid
# extrap - a logical, if TRUE then the data points are extrapolated.
# polDegree - polynomial degree, an integer ranging between 1 and 6.
# Value:
# A list with three elements, $x and $y which are vectors of length
# 'gridPoints' and $z which is a matrix of size 'gridPoints^2'.
# Example:
# x = runif(999)-0.5; y = runif(999)-0.5; z = cos(2*pi*(x^2+y^2))
# require(spatial)
# ans = krigeInterp(x, y, z, extrap = FALSE)
# persp(ans, theta = -50, phi = 30, col = "steelblue")
# Note:
# Requires Recommended R Package "spatial"
# FUNCTION:
if (!require(spatial, quietly = TRUE))
stop("\n -- Package spatial not available -- \n\n")
# Arguments:
if (is.list(x)) x = matrix(unlist(x), ncol = 3)
if (is.data.frame(x)) x = as.matrix.data.frame(x)
if (is.matrix(x)) {
z = x[, 3]
y = x[, 2]
x = x[, 1]
}
# Interpolate:
krige = surf.gls(np = polDegree, covmod = expcov,
x = x, y = y, z = z, d = 0.5, alpha = 1)
ans = prmat(krige,
xl = min(xo), xu = max(xo), yl = min(yo), yu = max(yo),
n = gridPoints-1)
# Extrapolate ?
# - this should be done more efficiently
if (!extrap) {
E = akimaInterp(x = x, y = y, z = z, gridPoints = gridPoints,
extrap = extrap)
ans$z[is.na(E$z)] = NA
}
class(ans) = "gridData"
# Return Value:
ans
}
################################################################################
|
