Matrix-class: Virtual Class "Matrix" of Matrices
In Matrix: Sparse and Dense Matrix Classes and Methods

Matrix-class

R Documentation

Virtual Class "Matrix" of Matrices

Description

The Matrix class is a class contained by all actual classes in the Matrix package. It is a “virtual” class.

Slots

Dim: an integer vector of length 2 giving the dimensions of the matrix.
Dimnames: a list of length 2. Each element must be NULL or a character vector of length equal to the corresponding element of Dim.

Methods

determinant: signature(x = "Matrix", logarithm = "missing"): and
determinant: signature(x = "Matrix", logarithm = "logical"): compute the (\log) determinant of x. The method chosen depends on the actual Matrix class of x. Note that det also works for all our matrices, calling the appropriate determinant() method. The Matrix::det is an exact copy of base::det, but in the correct namespace, and hence calling the S4-aware version of determinant().).
diff: signature(x = "Matrix"): As diff() for traditional matrices, i.e., applying diff() to each column.
dim: signature(x = "Matrix"): extract matrix dimensions dim.
dim<-: signature(x = "Matrix", value = "ANY"): where value is integer of length 2. Allows to reshape Matrix objects, but only when prod(value) == prod(dim(x)).
dimnames: signature(x = "Matrix"): extract dimnames.
dimnames<-: signature(x = "Matrix", value = "list"): set the dimnames to a list of length 2, see dimnames<-.
length: signature(x = "Matrix"): simply defined as prod(dim(x)) (and hence of mode "double").
show: signature(object = "Matrix"): show method for printing. For printing sparse matrices, see printSpMatrix.
zapsmall: signature(x = "Matrix"): typically used for "dMatrix": round() matrix entries such that (relatively) very small entries become zero exactly.
image: signature(object = "Matrix"): draws an image of the matrix entries, using levelplot() from package lattice.
head: signature(object = "Matrix"): return only the “head”, i.e., the first few rows.
tail: signature(object = "Matrix"): return only the “tail”, i.e., the last few rows of the respective matrix.

as.matrix, as.array: signature(x = "Matrix"): the same as as(x, "matrix"); see also the note below.
as.vector: signature(x = "Matrix", mode = "missing"): as.vector(m) should be identical to as.vector(as(m, "matrix")), implemented more efficiently for some subclasses.
as(x, "vector"), as(x, "numeric"): etc, similarly.
coerce: signature(from = "ANY", to = "Matrix"): This relies on a correct as.matrix() method for from.

There are many more methods that (conceptually should) work for all "Matrix" objects, e.g., colSums, rowMeans. Even base functions may work automagically (if they first call as.matrix() on their principal argument), e.g., apply, eigen, svd or kappa all do work via coercion to a “traditional” (dense) matrix.

Note

Loading the Matrix namespace “overloads” as.matrix and as.array in the base namespace by the equivalent of function(x) as(x, "matrix"). Consequently, as.matrix(m) or as.array(m) will properly work when m inherits from the "Matrix" class — also for functions in package base and other packages. E.g., apply or outer can therefore be applied to "Matrix" matrices.

Author(s)

Douglas Bates bates@stat.wisc.edu and Martin Maechler

Examples

slotNames("Matrix")

cl <- getClass("Matrix")
names(cl@subclasses) # more than 40 ..

showClass("Matrix")#> output with slots and all subclasses

(M <- Matrix(c(0,1,0,0), 6, 4))
dim(M)
diag(M)
cm <- M[1:4,] + 10*Diagonal(4)
diff(M)
## can reshape it even :
dim(M) <- c(2, 12)
M
stopifnot(identical(M, Matrix(c(0,1,0,0), 2,12)),
          all.equal(det(cm),
                    determinant(as(cm,"matrix"), log=FALSE)$modulus,
                    check.attributes=FALSE))

Matrix documentation built on April 12, 2025, 1:36 a.m.