# 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

Krig.make.W<- function( out, verbose=FALSE){

   if( verbose) { cat( "W", fill=TRUE) ; print( out$W)}
    
   if( out$nondiag.W) {
#
# create W from scratch or grab it from passed object

    if( is.null(out$W)){
         if( verbose){ print( out$wght.function.name)}
         W<- do.call( out$wght.function.name, 
                        c( list( x=out$xM), out$wght.args ))
#       adjust W based on diagonal weight terms 
#          
         W<- sqrt( out$weightsM)* t( sqrt(out$weightsM)*W) }
        else{ 
          W<-  out$W}
#
# symmetric square root
      eigen( W, symmetric=TRUE)-> temp
      W2<- temp$vectors%*% diag( sqrt( temp$values))%*% t( temp$vectors)
     return( list( W=W, W2=W2)) }
   
   else{
#
#  These are created only for use with default method to stay
#   consistent with nondiagonal elements.
    
   if(out$fixed.model){ 
            return(list( W=NULL, W2=NULL))}
        else{
     return(
        list( W=diag(out$weightsM), W2=diag(sqrt(out$weightsM)))) }

    }
   
}