Help with plot values

Question

Yogesh Bhambhwani 2020-12-17

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https://ww2.mathworks.cn/matlabcentral/answers/696660-help-with-plot-values

评论： Yogesh Bhambhwani 2020-12-17

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')

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Yogesh Bhambhwani 2020-12-17

So I read the document and looked at the Modify Lines After Creation section and I got an error saying that the vectorsmust be the same length

Daniel Pollard 2020-12-17

As I mentioned in my first comment, T_matrix has 5 elements. You need 100 T values to plot against 100 x values. Alan Stevens seems to have a better grasp of your problem and has left an answer.

I recommend checking out the Matlab onramp course if you're going to be using Matlab more. It's free, and introduces the basics of the programming language and is highly recommended you do that when you're starting out with Matlab.

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