Are the Dimnames dn NULL-like ?

Are the dimnames dn NULL-like?

is.null.DN(dn) is less strict than is.null(dn), because it is also true (TRUE) when the dimnames dn are “like” NULL, or list(NULL,NULL), as they can easily be for the traditional R matrices (matrix) which have no formal class definition, and hence much freedom in how their dimnames look like.

is.null.DN(dn)

Arguments

dn

dimnames() of a matrix-like R object.

Note

This function is really to be used on “traditional” matrices rather than those inheriting from Matrix, as the latter will always have dimnames list(NULL,NULL) exactly, in such a case.

Value

logical TRUE or FALSE.

Author

Martin Maechler

See also

is.null, dimnames, matrix.

Examples

m1 <- m2 <- m3 <- m4 <- m <-
    matrix(round(100 * rnorm(6)), 2, 3)
dimnames(m1) <- list(NULL, NULL)
dimnames(m2) <- list(NULL, character())
dimnames(m3) <- rev(dimnames(m2))
dimnames(m4) <- rep(list(character()),2)

m4 # prints absolutely identically to m
#>      [,1] [,2] [,3]
#> [1,]   28  -64  -60
#> [2,]   30 -131   -8

c.o <- capture.output
cm <- c.o(m)
stopifnot(exprs = {
    m == m1; m == m2; m == m3; m == m4
  identical(cm, c.o(m1));  identical(cm, c.o(m2))
  identical(cm, c.o(m3)); identical(cm, c.o(m4))
})

hasNoDimnames <- function(.) is.null.DN(dimnames(.))
stopifnot(exprs = {
    hasNoDimnames(m)
    hasNoDimnames(m1); hasNoDimnames(m2)
    hasNoDimnames(m3); hasNoDimnames(m4)
    hasNoDimnames(Matrix(m) -> M)
    hasNoDimnames(as(M, "sparseMatrix"))
})