How can I make a variable matrix?

I want to make variable matrices for my matrix equation: (2*A_11*r_i^2*C(1,2)*[U_1; ...; U_N])+(2*A_11*r_i*C(1,1)*[U_1; ...; U_N])-(2*A_11*[U_1; ...; U_N])+(A_11*r_i^2*W0*C(1,2)*[W_1; ...; W_N])+(((A_11*r_i)-(Nu*A_11*r_i))*W0*C(1,1)*[W_1; ...; W_N])=0 which are [U_1; ...; U_N] and [W_1; ...; W_N]. If anyone could help I would be thankful. A_11 is a scalar and r_i is a vector [0 0.0334 0.125 0.250 0.375 0.4665 0.500] and C(1,2) and C(1,1) are 7*7 matrices and W0 's are scalar. Actually this is a equation system which has 2 more equations and I need to solve it and use the results for W0 's and make a loop with some error function and also some boundary conditions. But for now i just wanna figure the part of variable matrix out first. Code I used is here and it is not right:

syms U

for N = 1:7

U(7,1) = U(N);

end

disp(U)

Answer 1

[Steven Lord]

You could do this:

syms U [7 1]
U

U = 

But be careful what you name your variable. Note that not only is U created but so are U1, U2, ...

whos

  Name        Size            Bytes  Class    Attributes

  U           7x1                 8  sym                
  U1          1x1                 8  sym                
  U2          1x1                 8  sym                
  U3          1x1                 8  sym                
  U4          1x1                 8  sym                
  U5          1x1                 8  sym                
  U6          1x1                 8  sym                
  U7          1x1                 8  sym                
  cmdout      1x33               66  char               

[mahdi]

Well yeah for example U_1 is relocation at r_1 and so on. And I also need that N cause I might want to change it to more grids and it will will have more U 's and W 's, so I should consider this as the right form of answer?

syms U [7 1]
for N = 1:7
    U(7,1) = U(N);
end
disp(U)

[mahdi]

nvm my last comment, your answer is good enough I think, thank you.

[Walter Roberson]

As I already showed, that code will end up with a vector of U_1 to U_6 and then an extra U_6 .

Each assignment to U(7,1) does not change any of the other locations in U. The first iteration replaces U(7,1) with U1. The second iteration replaces U(7,1) with U2. And so on to the 6th iteration replacing U(7,1) with U6. Then the 7th iteration is doing U(7,1) = U(7) but U(7) is currently U6 because of the previous iteration, so U(7,1) stays U6.

Answer 2

[Walter Roberson]

syms U [7 1]
for N = 1:7
    U(7,1) = U(N);
end
disp(U)

I suspect this is not what you want. I suspect what you want is just

syms U [7 1]
U

U =