What did i do wrong here?

L=1;      
alpha= 10^-3;  
T1=800;
T2=200;
x=0:0.01:L;
N=50;
t=0:5:25;
A_0=(T1+T2)/2;
Teaxct=zeros(length(x),length(t));

for m=1:length(x)  
for k=1:5:length(t)
  for n=1:(N)
       A_n(n)=(2*(T1-T2)/pi*(n))*(sin((pi/2)*(n)))*(cos((pi*n*m)/L))*(exp(-1*alpha*((pi*(n))/L)^2*k));
      Texact(m,k)=A_0+A_n(n)
   
     end
  end
          end

[KSSV]

Why three loops? Type error here in the variable Teaxct.

You can achieve what you want with meshgrid.

[Muhammad Umar Khan]

One for each variable

Answer 1

[Cris LaPierre]

In your third loop, the values of m and k do not change. This means the results of each loop are written to the same element of Texact, overwriting the previous value. The result is you only capture the final value in your third loop.

Your code also runs really slow because you are printing out the results of every single interation.

You also have a typo I suspect. You initialize Teaxct but then use Texact in your loops.

[Muhammad Umar Khan]

How to resolve it any idea

[Cris LaPierre]

Fix your typo, add a semicolon to the end of your Texact line, and then describe what your expected output size is. If you want to capture every value, you need to add a third dimension to Texact

Texact(m,k,n)= ...