And the other missing piece is that t() coerces the input vector to a 1-column matrix that can then be transposed and returned as a 1-row matrix (with a dim attribute).
-Christos > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Peter Dalgaard > Sent: Tuesday, November 11, 2008 1:31 PM > To: Daniel Høyer Iversen > Cc: r-devel@r-project.org > Subject: Re: [Rd] is.matrix > > Daniel Høyer Iversen wrote: > > a=c(1,1,2); > > is.matrix(a) gives FALSE > > is.matrix(t(a)) gives TRUE > > is.matrix(t(t(a))) gives TRUE > > > > Is this correct? Shouldn't all give FALSE? > > I think is.matrix should give FALSE when dimension is 1*n or n*1. > > No this is correct. is.matrix() returns TRUE if and only if > the argument has a two-dimensional 'dim' attribute, and > > > dim(a) > NULL > > dim(t(a)) > [1] 1 3 > > dim(t(t(a))) > [1] 3 1 > > (And is.array() depends on having a 'dim' attribute of > positive length, so > > > dim(a) <- 3 > > is.matrix(a) > [1] FALSE > > is.array(a) > [1] TRUE > > ) > > > -- > O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B > c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K > (*) \(*) -- University of Copenhagen Denmark Ph: > (+45) 35327918 > ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: > (+45) 35327907 > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
