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\name{is.null.DN}
\title{Are the Dimnames \code{dn} NULL-like ?}
%
\keyword{array}
\keyword{attribute}
\keyword{programming}
\keyword{utilities}
%
\alias{is.null.DN}
%
\description{
Are the \code{\link{dimnames}} \code{dn} \code{\link{NULL}}-like?
\code{is.null.DN(dn)} is less strict than \code{\link{is.null}(dn)},
because it is also true (\code{\link{TRUE}}) when the dimnames
\code{dn} are \dQuote{like} \code{NULL}, or \code{list(NULL,NULL)}, as
they can easily be for the traditional \R matrices
(\code{\link{matrix}}) which have no formal \code{\link{class}}
definition, and hence much freedom in how their \code{\link{dimnames}}
look like.
}
\usage{
is.null.DN(dn)
}
\arguments{
\item{dn}{\code{\link{dimnames}()} of a \code{\link{matrix}}-like \R
object.
}
}
\note{
This function is really to be used on \dQuote{traditional} matrices
rather than those inheriting from \code{\linkS4class{Matrix}}, as
the latter will always have dimnames \code{list(NULL,NULL)} exactly,
in such a case.
}
\value{
\code{\link{logical}} \code{\link{TRUE}} or \code{\link{FALSE}}.
}
%% \details{
%% }
\author{Martin Maechler}
\seealso{
\code{\link{is.null}},
\code{\link{dimnames}}, \code{\link{matrix}}.
}
\examples{
\dontshow{ % for R_DEFAULT_PACKAGES=NULL
library(stats, pos = "package:base", verbose = FALSE)
library(utils, pos = "package:base", verbose = FALSE)
}
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
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"))
})
}
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