Problem with BCtransform?

-----Original Message-----
From: r-sig-geo-bounces at stat.math.ethz.ch
[mailto:r-sig-geo-bounces at stat.math.ethz.ch]On Behalf Of Ruben Roa
Sent: 03 May 2005 10:44
To: R-sig-Geo at stat.math.ethz.ch
Subject: [R-sig-Geo] Problem with BCtransform?


Hi:

In geoR, when using BCtransform to back-transform the beta 
parameter into the space of the original data, like in

mean(BCtransform(rnorm(5000,mean=likfitobject$beta,sd=sqrt(li

kfitobject$beta.var)),lambda=XXX,inverse=TRUE))

i have noticed (in two applications) that the value of this 
mean is much smaller (2.3 and 3.4 times smaller) than
the mean of the kriged predictions, obtained with

mean(krig.object$predict)

even though geoR performs the back-transformation before kriging.

I would have thought that the two means (from 
back-transformed beta and from kriged predictions) would be
fairly similar. Of the two means the one that is closer to 
the mean of the raw data is the mean of the kriged 
predictions so i wonder maybe there is some problem with the 
BCtransform function when called by the
user? Or maybe there is something fundamental that i don't 
understand about the beta parameter (and thus its
back-transform)?

Thanks for clarifications.