lsparseMatrix-classes: Sparse logical matrices
Description
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 from the Class
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.