Concatenate matrix with for loop

Hi guys,

I got 3 matrices that I want to concatenate into one. Each matrix is 4x200. What I want to do is to create a matrix that is like matrix c:

a =

       8     1     6     5
       3     5     7     6
       4     9     2     7
  b =

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

c = [a(:,1) b(:,1);a(:,2) b(:,2);a(:,3) b(:,3);a(:,4) b(:,4)]

c =

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

I want to use a for loop but I couldn't get it to work. Your help will be appreciated. Thank you!

[Catherine]

I have tried:

t = 0;
g = 0;
for i = 1:size(a,2)
  for j = 1:size(a,1)
      c(t+1,g+1) = [a(j,i) b(j,i)];
      t = t+1;
  end
  t = 0;
  g = g+1;
end
g = 0;

But the error is dimension mismatch

[per isakson]

Why for-loop?

[Catherine]

I just thought it's the easiest way. If there is other ways, I am happy to try out as well. Thanks.

Answer 1

[Star Strider]

Try this:

c = [a(:) b(:)];

[Catherine]

Thanks! That's even easier.

[Star Strider]

As always, my pleasure!

Probably the easiest way is to create ‘v’ as a matrix, then concatenate it with the others:

v = repmat((1:size(a,1))', 1, size(a,2));
c = [v(:) a(:) b(:)];

Note the transpose operator ('). This creates ‘(1:size(a,1))’ as a column vector, necessary for the correct matrix creation.

This version of ‘v’ should work with any matrix ‘a’, since it is defined by the size dimensions of ‘a’.

[Catherine]

Great! that works well! Thank you

[Star Strider]

As always, my pleasure!