| lsparseMatrix-classes {Matrix} | R Documentation |
The lsparseMatrix class is a virtual class of sparse
matrices with TRUE/FALSE entries. Only the positions of the
elements that are TRUE are stored. These can be stored in the
``triplet'' form (classes lgTMatrix, lsTMatrix, and
ltTMatrix which really contain pairs, not triplets) or in
compressed column-oriented form (classes lgCMatrix,
lsCMatrix, and ltCMatrix) or in compressed row-oriented
form (classes lgRMatrix, lsRMatrix, and
ltRMatrix). The second letter in the name of these non-virtual
classes indicates general, symmetric, or triangular.
Objects can be created by calls of the form new("lgCMatrix",
...) and so on. More frequently objects are created by coercion of
a numeric sparse matrix to the logical form for use in
the symbolic analysis phase
of an algorithm involving sparse matrices. Such algorithms often
involve two phases: a symbolic phase wherein the positions of the
non-zeros in the result are determined and a numeric phase wherein the
actual results are calculated. During the symbolic phase only the
positions of the non-zero elements in any operands are of interest,
hence any numeric sparse matrices can be treated as logical sparse
matrices.
x:"logical", i.e., either
TRUE, NA, or FALSE.uplo:"character". Must be
either "U", for upper triangular, and "L", for lower
triangular. Present in the triangular and symmetric classes but not
in the general class.diag:"character". Must be
either "U", for unit triangular (diagonal is all ones), or
"N" for non-unit. The implicit diagonal elements are not
explicitly stored when diag is "U". Present in the
triangular classes only.p:"integer" of pointers, one
for each column (row), to the initial (zero-based) index of elements in
the column. Present in compressed column-oriented and compressed
row-oriented forms only.i:"integer" of length nnzero
(number of non-zero elements). These are the row numbers for
each TRUE element in the matrix. All other elements are FALSE.
Present in triplet and compressed column-oriented forms only.j:"integer" of length nnzero
(number of non-zero elements). These are the column numbers for
each TRUE element in the matrix. All other elements are FALSE.
Present in triplet and compressed column-oriented forms only.Dim:"integer" - the dimensions
of the matrix.signature(from = "dgCMatrix", to = "lgCMatrix")signature(x = "lgCMatrix"): returns the transpose
of x
the class dgCMatrix
(m <- Matrix(c(0,0,2:0), 3,5, dimnames=list(LETTERS[1:3],NULL)))
(lm <- (m > 1)) # lgC
!lm # no longer sparse
stopifnot(is(lm,"lsparseMatrix"),
identical(!lm, m <= 1))
data(KNex)
str(mmG.1 <- (KNex $ mm) > 0.1)# "lgC..."
table(mmG.1@x)# however with many ``non-structural zeros''
## from logical to nz_pattern -- okay when there are no NA's :
nmG.1 <- as(mmG.1, "nMatrix") # <<< has "TRUE" also where mmG.1 had FALSE
## from logical to "double"
dmG.1 <- as(mmG.1, "dMatrix") # has '0' and back:
lmG.1 <- as(dmG.1, "lMatrix") # has no extra FALSE, i.e. drop0() included
stopifnot(identical(nmG.1, as((KNex $ mm) != 0,"nMatrix")),
validObject(lmG.1), all(lmG.1@x),
# same "logical" but lmG.1 has no 'FALSE' in x slot:
all(lmG.1 == mmG.1))
class(xnx <- crossprod(nmG.1))# "nsC.."
class(xlx <- crossprod(mmG.1))# "dsC.." : numeric
is0 <- (xlx == 0)
mean(as.vector(is0))# 99.3% zeros: quite sparse, but
table(xlx@x == 0)# more than half of the entries are (non-structural!) 0
stopifnot(isSymmetric(xlx), isSymmetric(xnx),
## compare xnx and xlx : have the *same* non-structural 0s :
sapply(slotNames(xnx),
function(n) identical(slot(xnx, n), slot(xlx, n))))