
Last chance! 50% off unlimited learning
Sale ends in
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")
,
spMatrix()
, or
sparseMatrix(*, repr = "T")
.
i
:integer
row indices of non-zero
entries in 0-base, i.e., must be in 0:(nrow(.)-1)
.
j
:integer
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
vector - 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
:Object of class "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")
,
and typically coercion methods for more specific signatures, we
are not mentioning here.
Note that these are not guaranteed to continue to exist,
but rather you should use calls like as(x,
"CsparseMatrix")
, as(x, "generalMatrix")
,
as(x, "dMatrix")
, i.e. coercion to higher level virtual classes.
signature(from = "matrix", to = "dgTMatrix")
,
(direct coercion from tradition matrix).
signature(x = "dgTMatrix")
: plots an image of
x
using the levelplot
function
signature(x = "dgTMatrix")
: returns the transpose of
x
Class '>dgCMatrix
or the superclasses
'>dsparseMatrix
and
'>TsparseMatrix
; uniqTsparse
.
# NOT RUN {
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
## Triplet representation with repeated (i,j) entries
## *adds* the corresponding x's:
T2 <- new("dgTMatrix",
i = as.integer(c(1,1,0,3,3)),
j = as.integer(c(2,2,4,0,0)), x=10*1:5, Dim=4:5)
str(T2) # contains (i,j,x) slots exactly as above, but
T2 ## has only three non-zero entries, as for repeated (i,j)'s,
## the corresponding x's are "implicitly" added
stopifnot(nnzero(T2) == 3)
# }
Run the code above in your browser using DataLab