How to create array without cells

Hello!

How do you create an array that does not include cells?

for example

for i=1:3
   for j=1:3
      for k=1:3
         A(i,j,k) = i*j*k;
      end
   end
end

If I specify A(2,2,1) I would like to get the scalar 2*2*1=4. And if I want a vector, A(1,1,:)=[1 2 3]. Or A(2,2,:)=[4 8 12].

Hopefully I'm making sense here. Basically I want to be able to use A(1,1,:) in the same way you would use a Matrix B(1,:).

I would appreciate the help! /Kris

Answer 1

[Stephen23]

"Basically I want to be able to use A(1,1,:) in the same way you would use a Matrix B(1,:)."

MATLAB indexing works the same for all dimensions, so what is stopping you? When I run your code I get those exact values:

>> A(2,2,1)
ans =  4
>> A(1,1,:)
ans(:,:,1) =  1
ans(:,:,2) =  2
ans(:,:,3) =  3
>> A(2,2,:)
ans(:,:,1) =  4
ans(:,:,2) =  8
ans(:,:,3) =  12

Of course the second two example subarrays have size 1x1x3, because that is exactly the subarray that you are indexing. If you want 3x1 vectors, then use squeeze:

>> squeeze(A(1,1,:))
ans =
   1
   2
   3
>> squeeze(A(2,2,:))
ans =
    4
    8
   12

If you want vectors with other orientations, then use permute:

>> permute(A(1,1,:),[1,3,2])
ans =
   1   2   3
>> permute(A(2,2,:),[1,3,2])
ans =
    4    8   12

Of course you should also preallocate the array A before those loops, or write a vectorized version, e.g.:

[X,Y,Z] = ndgrid(1:3);
A = X.*Y.*Z

[Kristoffer Lindvall]

Awesome! Then my initial thought was correct, I just implemented it wrong in a sum. I will try using the squeeze command to see if it fixes my problem. This was really helpful. I will be playing around with this for a while so I can understand what's going on. Thanks!