how to arrange below code

i need to put the u1 u2 u3s in a loop and at the same time these i am trying to add 100 at the top and bottom of these matrixes.so that these 19*1 matrices becomes 21*1 matrices.the i want to plot for each u values.

clc;
clear;
n = 20;
L = 1;
dx = L/n;

%%
c = 1; 
C = 0.1;
dt = C*dx/c;
%%
cond = 0.0136;

b = cond*dt/(dx*dx);
%%
aa(1:n-2)=-b;

bb(1:n-1)=1.+2.*b;

cc(1:n-2)=-b;
%%
MM=(diag(bb,0)+diag(aa,-1)+diag(cc,1));
uu=zeros(19,1);
uu(1)  = b*100;
uu(19) = b*100;

u1 = inv(MM)*uu

u2 = inv(MM)*(uu+u1)

u3 = inv(MM)*(uu+u2)

u4 = inv(MM)*(uu+u3)

u5 = inv(MM)*(uu+u4)

u6 = inv(MM)*(uu+u5)

u7 = inv(MM)*(uu+u6)

Answer 1

[Jan]

With some guessing:

ux = zeros(19, 7);
ux(:, 1) = MM \ uu;   % Do not use inv(), see: doc inv
for k = 2:7
    ux(:, k) = MM \ (uu + ux(:, k-1));
end
pad    = repmat(100, 1, 7);
result = cat(1, pad, ux, pad);

Now result contains the column vectors.

See: TUTORIAL: EVAL . Do not hide indices in the names of variables.