mxn to MxN image interpolation

For a project I'm asked to use rough interpolation on an image which is originally mxn values and convert it to an MxN matrix where each value from mxn gets duplicated nearby. So if my mxn matrix is:

A = [1 2 3;4 5 6]

A m = 2, n = 3 matrix and I want to interpolate by M = 2, N = 2 then my new matrix would be m*M x n*N (4x6 in this example):

A_int = [1 1 2 2 3 3; 1 1 2 2 3 3; 4 4 5 5 6 6; 4 4 5 5 6 6]

The code I'm using works fine but I'm wondering if there is an easier way to do this. Essentially it'll copy row 1 and repeat it M times downwards, then take row 2 and copy it M times downward, etc. Then take column 1 and copy it N times to the right, then column 2, etc.

function M_save = sample_interpolation(M, m, n)
  [rows, cols, chs] = size(M); %determine the size of the incoming matrix

    rows_new = rows * m; %calculate the size of the new matrix
    cols_new = cols * n;

    M_save = uint8(zeros(rows_new, cols_new, chs)); %create a new matrix full of zeros

    a = 1:m:rows_new; %incremental value in step size of m 
    b = 1:n:cols_new; %incremental value in step size of n

    M_save(a,b,:) = M(:,:,:); %save each incremented value as the value from the original matrix

    for a = 1:m:rows_new %from the first row to the last skipping rows of zeros
        for i = 1:m-1 %from the current row to the n-1 row upstream
            M_save(i+a,:,:) = M_save(a,:,:); %save the value from a position in i+a
        end
    end
    for a = 1:n:cols_new %from the first col to the last skipping rows of zeros
        for i = 1:n-1 %from the current col to the m-1 row upstream
            M_save(:,a+i,:) = M_save(:,a,:); %save the value from a position in i+a
        end
    end

    figure('Name','Sample Effect')
    imshow(M_save)
    title([num2str(m),'x' ,num2str(n),' interpolation'])
end

Answer 1

[Guillaume]

Assuming you're on R2015b or later, this is extremely easy:

A = [1 2 3;4 5 6];
M = 2;
N = 2;

A_int = repelem(A, M, N)

[Aron]

Thank you so much. I knew there had to be a simpler way to do this and I appreciate your help. My for loops work, it's just convoluted.