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%#
%# fields is a package for analysis of spatial data written for
%# the R software environment.
%# Copyright (C) 2024 Colorado School of Mines
%# 1500 Illinois St., Golden, CO 80401
%# Contact: Douglas Nychka, douglasnychka@gmail.edu,
%#
%# 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
%##END HEADER
%##END HEADER
\name{spam2lz}
\alias{spind2spam}
\alias{spam2spind}
\alias{spind2full}
\alias{spam2full}
\title{Conversion of formats for sparse matrices}
\description{
Some supporting functions that are internal to fields top level
methods. These are used to convert between the efficient but
opaque format used by spam and more easily checked format based directly
on the row and column indices of non zero elements.
}
\usage{
spind2full(obj)
spam2full(obj)
spind2spam(obj, add.zero.rows=TRUE)
spam2spind(obj)
}
%- maybe also 'usage' for other objects documented here.
\arguments{
\item{obj}{
Either a list with the sparse index components (spind) or an
obj of class spam.}
\item{add.zero.rows}{If TRUE an entire row is zero add a hard zero value to the element in the first column for each zero row. The spam format requires at least one element in each row to have an explicit value. It is OK if this value is zero but one must be specified. }
}
\details{
The differencee in formats is best illustarted by an example:
A 4X5 sparse matrix:
\preformatted{
[,1] [,2] [,3] [,4] [,5]
[1,] 1 9 0 0 33
[2,] 0 0 0 26 34
[3,] 3 11 0 27 35
[4,] 0 12 20 0 36
}
spind format is a list with components "ind", "ra" and "da"
here is how the matrix above would be encoded:
\preformatted{
ind
I
[1,] 1 1
[2,] 1 2
[3,] 1 5
[4,] 2 4
[5,] 2 5
[6,] 3 1
[7,] 3 2
[8,] 3 4
[9,] 3 5
[10,] 4 2
[11,] 4 3
[12,] 4 5
da
[1] 4 5
ra
[1] 1 9 33 26 34 3 11 27 35 12 20 36
}
spam format is an S4 class with slot names
"entries", "colindices", "rowpointers" and "dimension".
entries
[1] 1 9 33 26 34 3 11 27 35 12 20 36
colindices
[1] 1 2 5 4 5 1 2 4 5 2 3 5
rowpointers
[1] 1 4 6 10 13
dimension
[1] 4 5
The row pointers are the position in the array of entries where the next row
starts.
NOTE: It is possible for the spind format to have a missing row of all
zeroes but this not allowed in spam format and produces an error message.
}
\author{Doug Nychka}
\seealso{as.spam}
\keyword{spatial}
% at least one, from doc/KEYWORDS
|
