R help - Apr 2009 - (hopefully) simple array op

I have a multidimensional array "a", for example,
> a
, , 1

     [,1] [,2]
[1,]    1    3
[2,]    2    4

, , 2

     [,1] [,2]
[1,]    5    7
[2,]    6    8

So a is 2x2x2.

I have another array "b", for example,
> b
     [,1] [,2]
[1,]    9   11
[2,]   10   12

So b is 2x2.

I want to "tack" b onto a so that b becomes a new "plane",
so to speak,
in a.  In other words, I want the result c to be:
> c
, , 1

     [,1] [,2]
[1,]    1    3
[2,]    2    4

, , 2

     [,1] [,2]
[1,]    5    7
[2,]    6    8

, , 3

     [,1] [,2]
[1,]    9   11
[2,]   10   12

I can think of a number of ways to do this, but they are all cumbersome.
Given R's facility with arrays and indices, it occurs to me that there
might be some "one-line" way to accomplish this.  Does anyone know if
there is?  Thanks.

--Sam

Regarding my last mail, I typed too soon.  Figure I can do
> a<-array(c(a,b),dim=c(2,2,3))
Seems to work fine.  But I would like to hear other ideas if you have
any.  In particular, I am going to have to do this operation over and
over.  That last index "3" will have to increase by one every time.
Seems like it would make for nicer code if I didn't have to worry about
that.  Thanks again.

Do you want abind?

http://cran.r-project.org/web/packages/abind/index.html

baptiste

On 15 Apr 2009, at 19:33, Cable, Samuel B Civ USAF AFMC AFRL/RVBXI  
wrote:
> I have a multidimensional array "a", for example,
>
>> a
> , , 1
>
>     [,1] [,2]
> [1,]    1    3
> [2,]    2    4
>
> , , 2
>
>     [,1] [,2]
> [1,]    5    7
> [2,]    6    8
>
> So a is 2x2x2.
>
> I have another array "b", for example,
>
>> b
>     [,1] [,2]
> [1,]    9   11
> [2,]   10   12
>
> So b is 2x2.
>
> I want to "tack" b onto a so that b becomes a new
"plane", so to
> speak,
> in a.  In other words, I want the result c to be:
>
>> c
> , , 1
>
>     [,1] [,2]
> [1,]    1    3
> [2,]    2    4
>
> , , 2
>
>     [,1] [,2]
> [1,]    5    7
> [2,]    6    8
>
> , , 3
>
>     [,1] [,2]
> [1,]    9   11
> [2,]   10   12
>
> I can think of a number of ways to do this, but they are all  
> cumbersome.
> Given R's facility with arrays and indices, it occurs to me that there
> might be some "one-line" way to accomplish this.  Does anyone
know if
> there is?  Thanks.
>
> --Sam
>
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_____________________________

Baptiste Augui?

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag