Create a 1D row vector (5,1) with middle elements = T.

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This is my code: I have problems with assigning the variable T to the 1D row vector.
N = 3;
a1=-2;
a2 = 1;
a3 = 1;
A = diag(a1*ones(1,N)) + diag(a2*ones(1,N-1),1) + diag(a3*ones(1,N-1),-1);
b = zeros(3,1); b(1,1) = -40; b(3,1) = -20;
T=A\b;
x=linspace(0,0.8,5);
Temperature= ones(5,1); Temperature(1,1)=40; Temperature (5,1)=20;
Temperature(2:n-1)=T;
plot(x,Temperature)
title('Temperature distribution between x=0 and x=0.8 ')
xlabel('x')
ylabel('Temperature')

Answers (1)

Karim
Karim on 28 Jun 2022
Edited: Karim on 28 Jun 2022
I guess this was only a typographical error, where you inserted the variable 'T' into 'temperature', see below for the adjusted code:
n = 100; % gridpoints
T1 = 100; % temp T1
T2 = 0; % temp T2
%construct a tridiagonal matrix
A=2*eye(n);
A=A-diag(ones(n-1,1),1);
A=A-diag(ones(n-1,1),-1);
A(1,:)=0;
A(1,1)=1; %Since the temperature at node 1 is known
A(n,:)=0;
A(n,n)=1; %Since the temperature at node n is known
% Construct a vector b with known temperatures
b=zeros(n,1);
b(1)=T1;
b(end)=T2;
x = linspace(0,0.8,n);
Temperature = A\b;
T = Temperature(2:end-1); % extract the middle temperatues for the ex
figure
plot(x,Temperature)
title('Temperature distribution between x=0 and x=0.8 ')
xlabel('x')
ylabel('Temperature')
  16 Comments
Ellie Matlab
Ellie Matlab on 28 Jun 2022
are you able to help me with adding an extra term to the vector b? This is my codes. But i failed the requirements, to my understanding as long i declare a varibale i sould be able to use it.
N = 3;
a1 =-2;
a2 = 1;
a3 = 1;
w=200000;
k=80.2;
deltax= 0.8/5-1;
A = diag(a1*ones(1,N)) + diag(a2*ones(1,N-1),1) + diag(a3*ones(1,N-1),-1);
b = zeros(3,1); b(1,1) = -40-(w/k)*deltax^2; b(3,1) = -20-(w/k)*deltax^2; b(2,1)=-(w/k)*deltax^2;
T=A\b;
x=linspace(0,0.8,5);
Temperature = ones(1,5);
Temperature(1,1)=40;
Temperature(1,5)=20;
Temperature(2:end-1)=T;
Temperature = transpose(Temperature);
plot(x,Temperature)
title('Temperature distribution between x=0 and x=0.8 ')
xlabel('x')
ylabel('Temperature')

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