# 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.null.function <- function(x, Z = NULL, drop.Z = FALSE, 
    m) {
    # default function to create matrix for fixed part of model
    #  x, Z, and drop.Z are required
    #  Note that the degree of the polynomial is by convention (m-1)
    # returned matrix must have the columns from Z last!
    #
    if (is.null(Z) | drop.Z) {
        return(fields.mkpoly(x, m = m))
    }
    else {
        return(cbind(fields.mkpoly(x, m = m), Z))
    }
}