MATLAB: How to append multiple matrices in a loop

for loop

hello,
my code-
 for ii=1:100
    if ii=1
        x=0;
    else
        for i=1:2:(((2^(ii-1))*2)-1)
            if i==1
                x=rand(2,2)
            elseif i==(((2^(ii-1))*2)-1)
                x=10*rand(2,2)
            else
                x=100*rand(2,2)
            end
            y=x
        end
    end
end
at y=x, i would like to append all the 2by2 matrices from the nested loop. how do i do that?

Best Answer

Using cat()
% following two are equavilant for concatenating along column
y = cat(1, y, x); 
y = [y; x];   
% following two are equavilant for concatenating along row
y = cat(2, y, x);
y = [y x];
Although if you can pre-allocate the space for y and use indexing, your code will be much faster. Read here: https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html
Related Question