Converting a 3D array to a 2D array in Matlab

Question

Suppose I have a 4x2x2 array such that

val(:,:,1) =

    1.0000   18.2190
    1.0000   15.4650
   12.0223   76.2841
   64.1669  104.7139

val(:,:,2) =

    1.0000   18.2190
   18.2190   18.6414
   11.5436   74.6475
   74.7046  110.4268

I am trying to "flatten" this 3D array into a 2D array so that it looks something like this

val(:,1) = 

    1.0000   
    18.2190
    1.0000   
    15.4650
    12.0223   
    76.2841
    64.1669
    104.7139

Is there a shorthand method for doing this so I can avoid using for-loops?

Answer 1

You can use a combination of permute() to rearrange your dimensions and then reshape() towards the desired format:

tmp = permute(val, [3, 2, 1]);
tmp2 = reshape(tmp, [size(tmp, 1), size(tmp, 2) * size(tmp, 3)]).'

tmp2 =

    1.0000    1.0000
   18.2190   18.2190
    1.0000   18.2190
   15.4650   18.6414
   12.0223   11.5436
   76.2841   74.6475
   64.1669   74.7046
  104.7139  110.4268

Or as a one-liner:

tmp2 = reshape(permute(val, [3, 2, 1]), [size(val, 3), size(tmp, 2) * size(val, 1)]).'