Combining matrices with different dimensions in an array in R

Question

I'd like to know if there is a way to combine two matrices with different dimensions into an array. I know there is the function abind(), but that function does not allow for different dimensions of the matrices. I need this because I use JAGS (with either R2jags or rjags) and these packages do not allow the data to be in list form. It does however work when I enter an array.

When I have the following two matrices:

a <- matrix(0, 3, 2)
b <- matrix(0, 4, 6)
a

     [,1] [,2]
[1,]    0    0
[2,]    0    0
[3,]    0    0

b

     [,1] [,2] [,3]
[1,]    0    0    0
[2,]    0    0    0
[3,]    0    0    0
[4,]    0    0    0

I would ideally have it like this:

abind(a,b, along = 3)

, , 1

     [,1] [,2]
[1,]    0    0
[2,]    0    0
[3,]    0    0

, , 2

     [,1] [,2] [,3]
[1,]    0    0    0
[2,]    0    0    0
[3,]    0    0    0
[4,]    0    0    0

score 0 · Answer 1 · edited Dec 18 '19 at 15:10

0

You can try to think of the matrices as one dimmensional arrays, which technically they are.

If you look at a matrix 'a' that is 3X3 and you try to access a[2][1] for example it is equivallent to a[2*3 + 1]. You can use this to just traverse your matrices and combine them.

edited Dec 18 '19 at 15:10

Aksen P

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answered Mar 17 '14 at 13:28

in need of help

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Can you demonstrate the a[2*3+1]? If I have the following matrix a <- matrix(1:6, 3, 2), then a[2][1] is 2. How does your solution result in the same value? – Jolanda Kossakowski Mar 17 '14 at 13:35
Do you mean a three dimensional matrix with sizes (6,3,2)? Have a look here http://stackoverflow.com/questions/5920944/how-are-3d-arrays-stored-in-c – in need of help Mar 17 '14 at 13:58
No a 2D matrix with values 1:6, 3 rows and 2 columns :) – Jolanda Kossakowski Mar 17 '14 at 14:01
In a 2D array with X rows and Y columns array a[i][j] = a[i*x + j] It means the same thing – in need of help Mar 17 '14 at 14:05

score -1 · Answer 2 · answered Mar 27 '20 at 03:32

-1

d=list(a,b)

i hope this is what do you want it's just like this

answered Mar 27 '20 at 03:32

nadjib amrouche

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The OP wants to combine matrices "into an array", not a list. – hplieninger Mar 27 '20 at 05:27

Combining matrices with different dimensions in an array in R

2 Answers2