| dgTMatrix-class {Matrix} | R Documentation |
The "dgTMatrix" class is the class of sparse
matrices stored as (possibly redundant) triplets. The internal
representation is not at all unique, contrary to the one for class
dgCMatrix.
Objects can be created by calls of the form new("dgTMatrix",
...), but more typically via as(*, "dgTMatrix").
i:"integer" - the row indices
of non-zero entries in 0-base, i.e., must be in
0:(nrow(.)-1).j:"integer" - the column
indices of non-zero entries. Must be the same length as slot
i and 0-based as well, i.e., in 0:(ncol(.)-1).x:"numeric" - the (non-zero)
entry at position (i,j). Must be the same length as slot
i. If an index pair occurs more than once the corresponding
values of slot x are added to form the element of the matrix.Dim:"integer" of length 2 -
the dimensions of the matrix.signature(e1 = "dgTMatrix", e2 = "dgTMatrix")signature(from = "dgTMatrix", to = "dgCMatrix")signature(from = "dgTMatrix", to = "dgeMatrix")signature(from = "dgTMatrix", to = "matrix")signature(from = "dgTMatrix", to = "dsCMatrix")signature(from = "dgTMatrix", to = "dtCMatrix")signature(from = "matrix", to = "dsTMatrix")signature(x = "dgTMatrix", y = "missing")
returns t(x) %*% x as an dsCMatrix object.signature(x = "dgTMatrix", y = "matrix"): ... signature(x = "dgTMatrix", y = "numeric"): ... signature(x = "dgTMatrix"): plots an image of
x using the levelplot functionsignature(x = "dgTMatrix"): returns the transpose of
x
Triplet matrices are a convenient form in which to construct sparse
matrices after which they can be coerced to
dgCMatrix objects.
Class dgCMatrix or the superclasses
dsparseMatrix and
TsparseMatrix;
m <- Matrix(0+1:28, nrow = 4)
m[-3,c(2,4:5,7)] <- m[ 3, 1:4] <- m[1:3, 6] <- 0
(mT <- as(m, "dgTMatrix"))
str(mT)
mT[1,]
mT[4, drop = FALSE]
stopifnot(identical(mT[lower.tri(mT)],
m [lower.tri(m) ]))
mT[lower.tri(mT,diag=TRUE)] <- 0
mT