# 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

`spind2full` <-
function(obj){

# create empty matrix and stuff at non zero locations
temp<- matrix( 0, obj$da[1],obj$da[2])
temp[ obj$ind] <- obj$ra

return( temp)
}

`spind2spam` <- function(obj){

# 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
 diff( c(0,ia, M+1) )-> hold

# Note: 1:M is the cumsum for elements. 
 ia<-(1:(M+1))[ hold!=0]

# check if there is a missing row. 
# if so stop -- because bad things happen ..
     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])] 
       stop(paste("Row(s)", ind.missing, "  missing in matrix") ) }

 return( new("spam", entries = obj$ra, colindices = obj$ind[,2], 
     rowpointers = ia,
        dimension = obj$da) )
}

`spam2spind` <-
function(obj){

# diff gives the number of nonzero elements in each row
I<-  rep( (1: obj@dimension[1]) , diff(obj@rowpointers) )

list( ind=cbind( I,obj@colindices), da= obj@dimension, ra= obj@entries)
}

`spam2full` <-
function(obj){

spind2full( spam2spind(obj))

}