How to create this matrix ?

I have a matrix whose size is 2x5x2 double and i have another matrix which is 2X5 double ,i just want to add together and make a simple matrix A,

in this A matrix there will be 2 rows ,total 15 column .

[Sam Chak]

Hi @Akash Pal

Can you really add matrices of incompatible sizes?

[Akash Pal]

yes i know its impossible but if there is any solution .

Answer 1

[John D'Errico]

It appears the request was to concatenate the two planes of A into one plane, and then concatenate another matrix to the columns of the result. So it would appear the word add was used in a suggestively wrong way. And since concatenation is the only way one could reasonably manipulate a 2x5x2 array, with another 2x5 array, to finally create a 2x15 result, that must surely be the case.

A = randi(5,[2,5,2])

A = 
A(:,:,1) =

     2     5     5     1     5
     2     4     5     5     2


A(:,:,2) =

     2     5     3     5     2
     2     5     4     1     5

B = randi([6,10],[2,5])

B = 2×5

9 10 7 9 6 7 8 7 7 6

So we have two matrices of the desires sizes.

Concatenation is easy. We could either first reshape A using the reshape function, or just extract the two planes of A. The latter is easier.

C = [A(:,:,1),A(:,:,2),B]

C = 2×15

2 5 5 1 5 2 5 3 5 2 9 10 7 9 6 2 4 5 5 2 2 5 4 1 5 7 8 7 7 6

However, reshape would have also worked, if we then used concatenation.

D = [reshape(A,[2,10]),B]

D = 2×15

2 5 5 1 5 2 5 3 5 2 9 10 7 9 6 2 4 5 5 2 2 5 4 1 5 7 8 7 7 6

As you can see, both operations worked nicely enough. If the matrix A had many planes, then reshape would be the better option.

Finally, it is crucially important to understand how the elements of a matrix are stored internally before/when you use reshape.

Answer 2

[Sam Chak]

@Akash Pal

Despite the Matrix Law forbids the operation, we can nearly always perform miracles with MATLAB, so long as you give the example of the desired output. Given M and N, how do you want to display the output of

M(:,:,1) = [1 2 3 4 5; 6 7 8 9 10];
M(:,:,2) = 2*[1 2 3 4 5; 6 7 8 9 10];
M

M = 
M(:,:,1) =

     1     2     3     4     5
     6     7     8     9    10


M(:,:,2) =

     2     4     6     8    10
    12    14    16    18    20

N = 3*M(:,:,1)

N = 2×5

3 6 9 12 15 18 21 24 27 30