Hello, i am a beginner in matlab, please if someone can help me to make a summation loop?

Knowing, that I have already calculated the values of the temperature in each point of space (1 to N) and as a function of time. So I need to calculate at each step of time the energy stored in my system in all the space points ..! The other parameters are constants. Help me and thank you in advance.

Answer 1

[Lilian Darracq]

Lets say you have stored your values into two differents vectors of length N :

theta_f = ...
theta_s = ...

Then you just have to type :

Energy = AH*deltaX*(epsilon_p*C_p_f*theta_f + (1-epsilon)*ro_s*_Cp_s*theta_s)*(T_h - T_amb); 
% Calculates the energy at each step and stores it into a vector

Total_Energy = sum(Energy,1) 
% Sums the energy vector to get the total energy

[Dawj Alami]

 for t=2:1441
     Tfctemp(t,1:N)= tridiag(a,b,c,f);
     Tsctemp(t,1:N)= tdma(r,s,q,g);
     % Energie srockéé
         Eng=(S*deltax*(Th-Tamb)*((por*rof*Cf*Tfctemp(t,1:N))+((1-por)*ros*Cs*Tsctemp(t,1:N))));
 end

Here is the loop I already programmed, how do I sum ?? Your answer does not work in my program

Knowing that the values of Tfctemp and Tsftemp have stored in my workspace

[Lilian Darracq]

Ok, i based my answer on the assumption that your theta vectors were unidimensionnal, but they're actually matrices.

Then this is how you want to get your result if i am not wrong :

Energy_total = zeros(1441,1);
 for t=2:1441
     Tfctemp(t,1:N)= tridiag(a,b,c,f);
     Tsctemp(t,1:N)= tdma(r,s,q,g);
     % Energie srockéé
     Eng=(S*deltax*(Th-Tamb)*((por*rof*Cf*Tfctemp(t,1:N))+((1-por)*ros*Cs*Tsctemp(t,1:N))));
     Energy_total(t) = sum(Eng,2);
     % This sums the vector Eng alongside its 2nd direction, which means that you sum on a line
 end

[Dawj Alami]

Yes it works very well now, thank you very much.

Also, can you help me calculate this sum !?? Double summation on time and space with N = 100

[Lilian Darracq]

If i understand this sum well, everything is constant except theta, which is a matrix, with n being columns index (space), and j being rows index (time).

The MATLAB function sum mainly takes two arguments : the vector/matrix you want to used, and the direction alongside which you want to sum.

Here you want to sum on columns (n) then rows (j). To do so, type this :

theta = ... % Matrix with tau rows and N columns
Energy_time = sum(U_pert*P*delta_X*theta*(Th-Tamb),2);
Energy_total = sum(Energy_time,1); 

% Or
Energy_total = sum(sum(U_pert*P*delta_X*theta*(Th-Tamb),2), 1);

% Or even faster
Energy_total = sum(sum(U_pert*P*delta_X*theta*(Th-Tamb));

[Dawj Alami]

Yes that's right, the program is working properly. Thank you so much for your help ^__^