MATLAB: Help with plot values

hw

Hi I am plotting my matrix and the x values are not what they are suppose to be. There is an example of the plot I have to make and the x-values should be from 0 to L (L is defined in my work) with 100 evenly spaced points. But I am getting that its from 1 to 5 can somepne help me please my work is below. My T_matrix is the y axis.
%initializing parameters
k=20;
P=0.1;
h=490;
A_c=4.4*10^-4;
L=0.08;
T_b=400;
T_inf=900;
nodes=5;
%build Coefficient and Constants (right hand side of eqn) matrices
T_1 = T_b;
dx = L/4;
x = dx*.5;
m = sqrt((h*P)/(k*A_c));
M = [ 1      0         0       0          0;
     -1 (2+(m*dx)^2)  -1       0          0;
      0      -1   (2+(m*dx)^2) -1         0;
      0       0       -1   (2+(m*dx)^2)   -1;
      0       0        0       -1    (2+(m*dx)^2)/2];
 
K = [T_b;
     (m*dx)^2*T_inf; 
     (m*dx)^2*T_inf; 
     (m*dx)^2*T_inf; 
     (m*dx)^2/2*T_inf];
T = M\K;
%solove matrix
T_matrix= T;
%define analytical solution
T_analytic= ((cosh(m*(L-x)))/(cosh(m*L)))*(T_b-T_inf)+T_inf;
%plot matrix and analytic solutions
plot(T_matrix,'r')

Best Answer

You need to define two different sets of x values. Your matrix solution results in 5 temperatures, so define
x = linspace(0,L,5)
and then plot T_matrix against this set of x's (preferably using points not lines).
You also need to define, say,
X = linspace(0,L,100)
and calculate the analytic values at these X's
T_analytic= ((cosh(m*(L-X)))/(cosh(m*L)))*(T_b-T_inf)+T_inf;
You can then plot XT_analytic against X (using lines).
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