```
# NOT RUN {
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"))
# }
```

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