R help - Mar 2011 - repeat matrix column within each array third dimension

Hello all,
I'm working with a matrix that will have varying dimensions.  It will
populate an array such that the number of matrix columns will determine the
number of 3rd dimension levels of the array.  Rows will be the same for both. 
For this example lets say the array will have 2 columns, but that's not
fixed.

dim(arr)<-c(dim(mat)[1],2,dim(mat)[2])

 I wish to repeat each matrix column in the 3rd dimension of an array as follows
in "desired appearance" below, but haven't quite got my generic
array() function right.  I need the equivalent of byrow=TRUE when filling in the
array.
thanks for all your help!


mat<-matrix(1:12,ncol=3)
mat
desired.arr<-array(NA,dim=c(dim(mat)[1],2,dim(mat)[2]))

#build array using generic code like this?
# need something like byrow=TRUE
array(rep(mat[1:dim(mat)[1],],each=dim(desired.arr)[2]),dim=dim(desired.arr))

# array needs to visually look as follows:
"desired appearance: "
array(c(rep(1:4,2),rep(5:8,2),rep(9:12,2)),dim=dim(desired.arr))


Michael Folkes

	[[alternative HTML version deleted]]

See ?aperm for changing the dimensions afterwards.

Uwe Ligges


On 08.03.2011 10:14, Folkes, Michael wrote:
> Hello all,
> I'm working with a matrix that will have varying dimensions.  It will
populate an array such that the number of matrix columns will determine the
number of 3rd dimension levels of the array.  Rows will be the same for both. 
For this example lets say the array will have 2 columns, but that's not
fixed.
>
> dim(arr)<-c(dim(mat)[1],2,dim(mat)[2])
>
>   I wish to repeat each matrix column in the 3rd dimension of an array as
follows in "desired appearance" below, but haven't quite got my
generic array() function right.  I need the equivalent of byrow=TRUE when
filling in the array.
> thanks for all your help!
>
>
> mat<-matrix(1:12,ncol=3)
> mat
> desired.arr<-array(NA,dim=c(dim(mat)[1],2,dim(mat)[2]))
>
> #build array using generic code like this?
> # need something like byrow=TRUE
>
array(rep(mat[1:dim(mat)[1],],each=dim(desired.arr)[2]),dim=dim(desired.arr))
>
> # array needs to visually look as follows:
> "desired appearance:"
> array(c(rep(1:4,2),rep(5:8,2),rep(9:12,2)),dim=dim(desired.arr))
>
>
> Michael Folkes
>
> 	[[alternative HTML version deleted]]
>
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