# fields, Tools for spatial data
# Copyright 2004-2007, 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")