Generator matrix for repetition coding

Hello. I would like to be able to make generator repetition matrices for given vectors. If I have the vector

u = [1 0 0 1]

with parameter q=3(how many times every bit will be repeated), I would like to take from matlab the G matrix

G = [1 1 1 0 0 0 0 0 0 0 0 0;
     0 0 0 1 1 1 0 0 0 0 0 0;
     0 0 0 0 0 0 1 1 1 0 0 0;
     0 0 0 0 0 0 0 0 0 1 1 1];

So the multiplication

c = u*G

gives

c = [1 1 1 0 0 0 0 0 0 1 1 1];

So, I would like to give u,q inputs to matlab and get G for very big matrices. Basically, the creation of G matrix requires only the length of u and the q. If the length of u=3 and q=2, we have

 G = [1 1 0 0 0 0;
      0 0 1 1 0 0;
      0 0 0 0 1 1];

Answer 1

[Azzi Abdelmalek]

Edited

u=3;
q=2;
C=zeros(u,q*u);
jj=1:q;
for k=1:u
  C(k,jj)=1;
  jj=jj+q;
end
C

%Or

u=4
q=3
C=zeros(u,q*u)
jj=1:q
x=reshape(repmat(1:u,q,1),[],1)'
y=1:q*u
idx=sub2ind(size(C),x,y)
C(idx)=1

%Or

u=4
q=3
d=mat2cell(ones(1,q*u),1,q*ones(1,u))
out=blkdiag(d{:})

[freebil]

Thanks for the answer, but I would like something without for loop because the matrices will be with length 10^5.

[Azzi Abdelmalek]

Look at edited answer

[freebil]

Thank you very much for your answer!

[Azzi Abdelmalek]

u=10^5;
q=3;
C=sparse(u,q*u);
jj=1:q;
x=reshape(repmat(1:u,q,1),[],1)';
y=1:q*u;
idx=sub2ind(size(C),x,y);
C(idx)=1;