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Matrix {Matrix}

Construct a Classed Matrix


Construct a Matrix of a class that inherits from Matrix.


Matrix(data=NA, nrow=1, ncol=1, byrow=FALSE, dimnames=NULL,
       sparse = NULL, doDiag = TRUE, forceCheck = FALSE)


an optional numeric data vector or matrix.
when data is not a matrix, the desired number of rows
when data is not a matrix, the desired number of columns
logical. If FALSE (the default) the matrix is filled by columns, otherwise the matrix is filled by rows.
a dimnames attribute for the matrix: a list of two character components. They are set if not NULL (as per default).
logical or NULL, specifying if the result should be sparse or not. By default, it is made sparse when more than half of the entries are 0.

Note that when the resulting matrix is diagonal (“mathematically”), sparse=FALSE results in a diagonalMatrix, unless doDiag=FALSE as well, see the first examples.

only when sparse = FALSE, logical indicating if a diagonalMatrix object should be considered (default). Otherwise, in such a case, a dense (symmetric) matrix will be returned.
logical indicating if the checks for structure should even happen when data is already a "Matrix" object.


If either of nrow or ncol is not given, an attempt is made to infer it from the length of data and the other parameter. Further, Matrix() makes efforts to keep logical matrices logical, i.e., inheriting from class lMatrix, and to determine specially structured matrices such as symmetric, triangular or diagonal ones. Note that a symmetric matrix also needs symmetric dimnames, e.g., by specifying dimnames = list(NULL,NULL), see the examples.

Most of the time, the function works via a traditional (full) matrix. However, Matrix(0, nrow,ncol) directly constructs an “empty” sparseMatrix, as does Matrix(FALSE, *).

Although it is sometime possible to mix unclassed matrices (created with matrix) with ones of class "Matrix", it is much safer to always use carefully constructed ones of class "Matrix".


Returns matrix of a class that inherits from "Matrix". Only if data is not a matrix and does not already inherit from class Matrix are the arguments nrow, ncol and byrow made use of.

See Also

The classes Matrix, symmetricMatrix, triangularMatrix, and diagonalMatrix; further, matrix.

Special matrices can be constructed, e.g., via sparseMatrix (sparse), bdiag (block-diagonal), bandSparse (banded sparse), or Diagonal.


Matrix(0, 3, 2)             # 3 by 2 matrix of zeros -> sparse
Matrix(0, 3, 2, sparse=FALSE)# -> 'dense'
Matrix(0, 2, 2, sparse=FALSE)# diagonal !
Matrix(0, 2, 2, sparse=FALSE, doDiag=FALSE)# -> dense
Matrix(1:6, 3, 2)           # a 3 by 2 matrix (+ integer warning)
Matrix(1:6 + 1, nrow=3)
## logical ones:
Matrix(diag(4) >  0)# -> "ldiMatrix" with diag = "U"
Matrix(diag(4) >  0, sparse=TRUE)# -> sparse...
Matrix(diag(4) >= 0)# -> "lsyMatrix" (of all 'TRUE')
## triangular
l3 <- upper.tri(matrix(,3,3))
(M <- Matrix(l3))  # -> "ltCMatrix"
Matrix(! l3)# -> "ltrMatrix"
as(l3, "CsparseMatrix")
Matrix(1:9, nrow=3,
       dimnames = list(c("a", "b", "c"), c("A", "B", "C")))
(I3 <- Matrix(diag(3)))# identity, i.e., unit "diagonalMatrix"
str(I3) # note the empty 'x' slot
(A <- cbind(a=c(2,1), b=1:2))# symmetric *apart* from dimnames
Matrix(A)                    # hence 'dgeMatrix'
(As <- Matrix(A, dimnames = list(NULL,NULL)))# -> symmetric
stopifnot(is(As, "symmetricMatrix"),
          is(Matrix(0, 3,3), "sparseMatrix"),
          is(Matrix(FALSE, 1,1), "sparseMatrix"))

Documentation reproduced from package Matrix, version 1.1-2. License: GPL (>= 2)