Storing Iteration Results in Matlab - matlab

Question

I have the code below.
for k=40:10:80
T(k)=273.15+k;
z=[0.2 0.2 0.2 0.4];
W_PR=0.245;
C=4;
omega=[0.344 0.467 0.578 0.789];
Tc=[600 700 500 570];
Pc=[50 70 58 76];
for c=1:C
x_PR(1,c)=z(c)/(1+W_PR*(K_PR(c)-1));
x_PR(2,c)=K_PR(c)*x_PR(1,c);
end
for c=1:C
kappa_PR=0.37464+1.54226.*omega(c)-0.26992.*omega(c).^2;
alpha_PR=(1+kappa_PR.*(1-sqrt(T(k)./Tc(c)))).^2;
a_PR(c,c)=0.45724.*R.^2.*Tc(c).^2./Pc(c).*alpha_PR;
b_PR(c)=0.07780*R.*Tc(c)./Pc(c);
end
for c=2:C
for n=1:(c-1)
a_PR(c,n)=sqrt(a_PR(c,c).*a_PR(n,n));
a_PR(n,c)=a_PR(c,n);
end
end
for c=1:C
A_PR(c,c)=a_PR(c,c).*P./(R.*T(k)).^2;
B_PR(c)=b_PR(c).*P./(R.*T(k));
end
for c=1:C
Z(c,c)=A_PR(c,c)./5;
V(c)=B_PR(c).*6;
end
end
Each time I run the code, I want result for Z and V at each T(k).
The code as it is only gives result for one T value though I want it to run the loop and give result for Z and V for all T(k).

Answer 1

You might want to define some of your parameters outside of your main loop to, at the very least, preallocate storage.
Z_store = ones(C,C,5); % if you want to use a 3d matrix
and
V_store = ones(5,C);
The new function:
function [Z_store V_store] = SO_test1()
z=[0.2 0.2 0.2 0.4];
W_PR=0.245;
C=4;
omega=[0.344 0.467 0.578 0.789];
Tc=[600 700 500 570];
Pc=[50 70 58 76];
R=8.314;
P=20;
Z_store = ones(C,C,5);
V_store = ones(5,C);
K_PR=[1.546e-2, 0.456, 1.432e2, 14.32];
iter = 0;
for k=40:10:80
T(k)=273.15+k;
for c=1:C
x_PR(1,c)=z(c)/(1+W_PR*(K_PR(c)-1));
x_PR(2,c)=K_PR(c)*x_PR(1,c);
kappa_PR=0.37464+1.54226.*omega(c)-0.26992.*omega(c).^2;
alpha_PR=(1+kappa_PR.*(1-sqrt(T(k)./Tc(c)))).^2;
a_PR(c,c)=0.45724.*R.^2.*Tc(c).^2./Pc(c).*alpha_PR;
b_PR(c)=0.07780*R.*Tc(c)./Pc(c);
end
for c=2:C
for n=1:(c-1)
a_PR(c,n)=sqrt(a_PR(c,c).*a_PR(n,n));
a_PR(n,c)=a_PR(c,n);
end
end
for c=1:C
A_PR(c,c)=a_PR(c,c).*P./(R.*T(k)).^2;
B_PR(c)=b_PR(c).*P./(R.*T(k));
Z(c,c)=A_PR(c,c)./5;
V(c)=B_PR(c).*6;
end
iter = iter + 1;
Z_store(:,:,iter) = Z;
V_store(iter,:) = V;
end
end

Answer 2

Your result matrices V and Z need to have higher dimension. From your code you only assign values to Z in the form
Z(c,c) = value
and V in the form
V(c) = value
thus it appears that your Z is simply a 2d matrix who only ever has diagonal entries defined and V is just a simple vector. Your iteration runs over all values of your loop variable k but each time you are overwriting the current values within these arrays. Consider making V a 2D array and Z a 3D array so that they have the capacity to store the results at a separate index for each value of the iteration variable k