# [R] Stacking matrix columns

Eric Berger er|cjberger @end|ng |rom gm@||@com
Sun Aug 6 09:33:31 CEST 2023

```Stacking columns of a matrix is a standard operation in multilinear
algebra, usually written as the operator vec().
I checked to see if there is an R package that deals with multilinear
algebra. I found rTensor, which has a function vec().
So, yet another way to accomplish what you want would be:

> library(rTensor)
> vec(as.tensor(x))

Eric

On Sun, Aug 6, 2023 at 5:05 AM Bert Gunter <bgunter.4567 using gmail.com> wrote:
>
> Or just dim(x) <- NULL.
> (as matrices in base R are just vectors with a dim attribute stored in
> column major order)
>
> ergo:
>
> > x
>  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20
> > x<- 1:20  ## a vector
> > is.matrix(x)
> [1] FALSE
> > dim(x) <- c(5,4)
> > is.matrix(x)
> [1] TRUE
> > attributes(x)
> \$dim
> [1] 5 4
>
> > ## in painful and unnecessary detail as dim() should be used instead
> > attr(x, "dim") <- NULL
> > is.matrix(x)
> [1] FALSE
> > x
>  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20
>
> ## well, you get it...
>
> -- Bert
>
> On Sat, Aug 5, 2023 at 5:21 PM Iris Simmons <ikwsimmo using gmail.com> wrote:
> >
> > You could also do
> >
> > dim(x) <- c(length(x), 1)
> >
> > On Sat, Aug 5, 2023, 20:12 Steven Yen <styen using ntu.edu.tw> wrote:
> >
> > > I wish to stack columns of a matrix into one column. The following
> > > matrix command does it. Any other ways? Thanks.
> > >
> > >  > x<-matrix(1:20,5,4)
> > >  > x
> > >       [,1] [,2] [,3] [,4]
> > > [1,]    1    6   11   16
> > > [2,]    2    7   12   17
> > > [3,]    3    8   13   18
> > > [4,]    4    9   14   19
> > > [5,]    5   10   15   20
> > >
> > >  > matrix(x,ncol=1)
> > >        [,1]
> > >   [1,]    1
> > >   [2,]    2
> > >   [3,]    3
> > >   [4,]    4
> > >   [5,]    5
> > >   [6,]    6
> > >   [7,]    7
> > >   [8,]    8
> > >   [9,]    9
> > > [10,]   10
> > > [11,]   11
> > > [12,]   12
> > > [13,]   13
> > > [14,]   14
> > > [15,]   15
> > > [16,]   16
> > > [17,]   17
> > > [18,]   18
> > > [19,]   19
> > > [20,]   20
> > >  >
> > >
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