R/LKrigSetupAlpha.R

In LatticeKrig: Multi-Resolution Kriging Based on Markov Random Fields

# LatticeKrig  is a package for analysis of spatial data written for
# the R software environment .
# Copyright (C) 2016
# University Corporation for Atmospheric Research (UCAR)
# Contact: Douglas Nychka, nychka@ucar.edu,
# National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307-3000
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with the R software environment if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
# or see http://www.r-project.org/Licenses/GPL-2

LKrigSetupAlpha <- function(object, ...){
  UseMethod("LKrigSetupAlpha")
}

LKrigSetupAlpha.default<- function( object, ...){
   alpha <- object$alpha
   nlevel <- object$nlevel
# some obvious defaults for alpha to simplify calls from LatticeKrig or LKrig. 
# if alpha varies over space then set the scalat parameters to one.    
   if( is.na(alpha[1]) & !is.null(object$alphaObject)){
     alpha<- rep( 1.0, nlevel)
   }
   if( !is.null( object$nu)){
     thetaL<-  2^(-1*(1:nlevel))
     alpha<- thetaL^(2*object$nu)
     # normalize to sum to 1
     alpha<- alpha/ sum( alpha)
   }
#   
# more defaults for scalar alphas    
   if( is.na(alpha[1])&  nlevel==1 ) { alpha<- 1.0 }
   scalar.alpha <- !is.list(alpha) 
   if (scalar.alpha & (nlevel != 1) & (length(alpha) == 1)){
                stop( "Only one alpha specifed for multiple levels")}     
# coerce alpha to a list if it is passed as something else
    if (!is.list(alpha)) {
        alpha <- as.list(alpha)
    }
    return( alpha )
 }