R/LKrig.spind2spam.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

LKrig.spind2spam <- function(obj, add.zero.rows = TRUE) {
    # Check if there is a missing row. If so either stop or fill in these row with a zero value
    if (length(unique(obj$ind[, 1])) < obj$da[1]) {
        # The offending rows -- concise but inpentrable R code!
        ind.missing <- (1:obj$da[1])[-unique(obj$ind[, 1])]
        N.missing <- length(ind.missing)
        if (!add.zero.rows) {
            cat(N.missing, " missing row(s)", fill = TRUE)
            stop("Can not coerce to spam format with add.zero.rows==FALSE")
        }
        else {
            # put a hard zero in the first column of each missing row
            obj$ind <- rbind(obj$ind, cbind(ind.missing, rep(1, 
                N.missing)))
            obj$ra <- c(obj$ra, rep(0, N.missing))
        }
    }
    # sort on rows and then columns to make sure they are in order
    ii <- order(obj$ind[, 1], obj$ind[, 2])
    #    shuffle indices and entries so they are in row order
    obj$ind <- obj$ind[ii, ]
    obj$ra <- obj$ra[ii]
    ia <- obj$ind[, 1]
    # define total number of nonzero elements
    M <- length(ia)
    # find places where rows change
    hold <- diff(c(0, ia, M + 1))
    # Note: 1:M is the cumsum for elements.
    ia <- (1:(M + 1))[hold != 0]
    return(new("spam", entries = as.numeric(obj$ra), colindices = as.integer(obj$ind[, 
        2]), rowpointers = as.integer(ia), dimension = as.integer(obj$da)))
}