https://github.com/cran/fields
Tip revision: 370c1161f275c7f191e9326102bfd61cae62d545 authored by Douglas Nychka on 11 May 2017, 17:23:03 UTC
version 8.15
version 8.15
Tip revision: 370c116
vgram.test.R
# fields, Tools for spatial data
# Copyright 2004-2011, Institute for Mathematics Applied Geosciences
# University Corporation for Atmospheric Research
# Licensed under the GPL -- www.gpl.org/licenses/gpl.html
# test of vgram
library( fields)
options(echo=FALSE)
data( ozone2)
y<- ozone2$y[16,]
x<- ozone2$lon.lat
vgram( x, y, lon.lat=TRUE)-> out
# compute "by hand"
outer( y, y ,"-")-> hold
hold<- .5*hold^2
rdist.earth( x,x)-> hold2
col( hold2)> row( hold2)-> upper
hold<- hold[upper]
hold2<- hold2[upper]
order( hold2)-> od
hold2<- hold2[od]
hold<- hold[od]
ind<- is.na(hold)
hold<- hold[!ind]
hold2<- hold2[!ind]
test.for.zero( hold, out$vgram, tag="vgram single time")
# multiple times including NAs at some times
y<- t(ozone2$y[16:18,])
x<- ozone2$lon.lat[,]
out<- vgram( x, y, lon.lat=TRUE)
N<- nrow( y)
hold<- cbind(c(outer( y[,1], y[,1],"-")),
c(outer( y[,2], y[,2],"-") ),
c(outer(y[,3], y[,3],"-")) )
hold<- .5*hold^2
hold<- rowMeans( hold, na.rm=TRUE)
hold<- matrix( hold, N,N)
rdist.earth( x,x)-> hold2
col( hold2)> row( hold2)-> upper
hold<- hold[upper]
hold2<- hold2[upper]
order( hold2)-> od
hold2<- hold2[od]
hold<- hold[od]
ind<- is.na(hold)
hold<- hold[!ind]
hold2<- hold2[!ind]
test.for.zero( hold, out$vgram, tag="vgram more than one time point")
# test covariogram versus correlogram
y<- ozone2$y[16,]
x<- ozone2$lon.lat
sigma2 = var(y, na.rm=TRUE)
lookCov = vgram(x, y, lon.lat=TRUE, type="covariogram")
lookCor = vgram(x, y, lon.lat=TRUE, type="correlogram")
test.for.zero(lookCov$vgram*(1/sigma2), lookCor$vgram, tag="correlogram versus covariogram")
# test cross-covariogram versus cross-correlogram
sigma2 = var(y, na.rm=TRUE)
lookCov = crossCoVGram(x, x, y, y, lon.lat=TRUE, type="cross-covariogram")
lookCor = crossCoVGram(x, x, y, y, lon.lat=TRUE, type="cross-correlogram")
test.for.zero(lookCov$vgram*(1/sigma2), lookCor$vgram, tag="correlogram versus covariogram")