reshape many submatrices to form a new matrix

I have got a 450 by 450 matrix. I need to reshape every 30 by 30 submatrix to become a 1 by 900 matrix. Therefore, there are 225 1 by 900 matrices. Then I have to group those 225 matrices to become a 225 by 900 matrix. At this moment I have got something like this to extract every 30 by 30 matrices.

for i=1:30:450
      for j =1:30:450
          G= m((i:i+29),(j:j+29));
      end
end

But I have no ideas how to reshape those matrices to become 1 by 900 matrices to form a 225 by 900 matrix. Hope somebody can help, thank you.

[Azzi Abdelmalek]

Your code doesn't work. And you have to precise the order of your sub matrices (horizontal or vertical)

Answer 1

[Azzi Abdelmalek]

A=rand(450);
ii1=1:30:450;
ii2=1:30:450;
[x,y]=meshgrid(ii1,ii2);
B=arrayfun(@(ii,jj) reshape(A(ii:ii+29,jj:jj+29),1,[]),x,y,'un',0)
out=cell2mat(B(:))

another way is to switch x and y

B=arrayfun(@(ii,jj) reshape(A(ii:ii+29,jj:jj+29),1,[]),y,x,'un',0)

Answer 2

[Andrei Bobrov]

From tricks by Peter J. Acklam:

s1 = size(A);
s2 = [30 30];
m = s1./s2;
p1 = reshape(A,s2(1),m(1),s2(2),[]);
p2 = permute(p1,[1 3 4 2]);
out = reshape(p2,prod(s1),[])';

or with bsxfun

s = size(A);
m = [30 30];
k = bsxfun(@plus,(0:m(1)-1)',(0:m(2)-1)*s(1));
l = bsxfun(@plus,(1:m(1):s(1))',(0:m(2):s(2)-1)*s(1))';
out = A(bsxfun(@plus,l(:),k(:)'));