Assign letters as matrices; inputs

I try to write a function that takes as its input argument a scalar integer and returns Q, a 2n-by-2n matrix. Q consists of four n-by-n submatrices. The elements of the submatrix in the top left corner are all 1s, the elements of the submatrix at the top right are 2s, the elements in the bottom left are 3s, and the elements in the bottom right are 4s. My main problem is that I do not know how to assign 's' in the matrix. Any help will be appreciated

function Q = quadrants( n )
M=zeros(2*n)
s = sym('s')
for i=1:n
  for j=1:n
    M(i,j)=s
  end
end
for i=1:3
  for j=(n+1): end
    M(i,j)=2*s
  end
end
for i=(n+1):2*n
  for j=1:n
    M(i,j)=3*s
  end
end
for i=(n+1):2*n
  for j=(n+1):2*n
  end
end
end

[Thorsten]

You can create a numerical matrix without for loops using

O = ones(n);
Q = [O 2*O; 3*O 4*O]

[dpb]

Why not move this to Answer so OP can accept it?

[Guillaume]

Possibly because the OP question is about symbolic variables.

Answer 1

[Joachim Schlosser]

You need to create the matrix as a symbolic matrix:

M=sym('s',[n,n])