Adding matrices to a 3D matrix in a specific order

Say I have a 3D matrix 50x50x100

Now I want to add another matrix to make it 50x50x101, however I want the new matrix to go in a particular position e.g. the 10th out of the 101 matrices.

How can I achieve this?

Answer 1

[Stephen23]

This is easy using MATLAB indexing. Here is an example with 2D matrices, to show how indexing can be used to insert values in particular locations of a new matrix:

>> M = [1,2,3;4,5,6] % original matrix
M =
   1   2   3
   4   5   6
>> N(:,[1,3:4]) = M % insert M into cols 1,3 and 4 of N
N =
   1   0   2   3
   4   0   5   6
>> N(:,2) = [Inf,NaN] % insert into col 2 of N
N =
     1   Inf     2     3
     4   NaN     5     6

And here is a 3D example as well:

>> X = reshape([1,2,3,4,5,6],1,2,3); % original array
>> Y(:,:,[1,3:4]) = X;  % insert into pages 1, 3 and 4 of Y
>> Y(:,:,2) = [Inf,NaN] % insert into page 2 of Y
Y(:,:,1) =
   1   2
Y(:,:,2) =
   Inf   NaN
Y(:,:,3) =
   3   4
Y(:,:,4) =
   5   6

More information on indexing:

http://www.mathworks.com/help/matlab/math/matrix-indexing.html

http://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html