How can I get the value by choosing 't' and 'x'? ,How should I set the graph range?

L = 30;
n = 10;
T0=500;
T1s=300;
T2s=400;

dx=L/n;

alpha=0.000085;

t_final=4800;

dt=0.1;

x = dx/2:dx:L-dx/2;

T = ones(n,1)*T0;

dTdt=zeros(n,1);

t = 0:dt:t_final;

for j = 1:length(t)
    for i = 2:n-1
        dTdt(i)=alpha*(-(T(i)-T(i-1))/dx^2+(T(i+1)-T(i))/dx^2);
    end
    dTdt(1)=alpha*(-(T(1)-T1s)/dx^2+(T(2)-T(1))/dx^2);
    dTdt(n)=alpha*(-(T(n)-T(n-1))/dx^2+(T2s-T(n))/dx^2);
    T=T+dTdt*dt;
    figure(1)
    plot(x,T)
    xlabel('distance(n)')
    ylabel('Temperature(\circC)')
    pause(1)
    
    
end

Answer 1

[J Chen]

Move the plot command outside the loop. Store the calculation at each time step in a buffer. For example:

hist = nan(n,length(t));
for
   .
   .
   hist(:,j) = T;
end
plot(:,400)

Answer 2

[VBBV]

L = 30;
n = 10;
T0=500;
T1s=300;
T2s=400;

dx=L/n;

alpha=0.000085;

t_final=4800;

dt=300; % use a coarse timestep for faster loop execuetion 

x = dx/2:dx:L-dx/2;

T = ones(n,1)*T0;

dTdt=zeros(n,1);

t = 0:dt:t_final;

for j = 1:length(t)
    hold on  % use a hold on command
    for i = 2:n-1
        dTdt(i)=alpha*(-(T(i)-T(i-1))/dx^2+(T(i+1)-T(i))/dx^2);
    end
    dTdt(1)=alpha*(-(T(1)-T1s)/dx^2+(T(2)-T(1))/dx^2);
    dTdt(n)=alpha*(-(T(n)-T(n-1))/dx^2+(T2s-T(n))/dx^2);
    T=T+dTdt*dt;
    %figure(1)
    plot(x,T)  
    
end
xlabel('distance(n)');  ylabel('Temperature(\circC)')

Use a hold on command at the beginning of first for loop. Assume a coarser time step for faster loop execution.