# Keep getting error message on my ODE function

6 views (last 30 days)
I am currently working on coding polymerization of PLA in a batch reactor keep getting error message. My professor helped my group get to this point but eveytime we run it we get,
Error using horzcat
Dimensions of arrays being concatenated are not consistent.
We have tried everything we can think of to fix this problem but we arent sure why this is happening or how to fix it.
u0=[P0 zeros(N,1) 0] ;
T = 180+273.15; %Temperature [K]
Keq=10;
%% Calculations
lk1=-(6810.3/T)+6.1928
k1=exp(lk1) %rate constant for Polymerization (L/mol*s)
km1=k1/Keq %rate constant for depolymerization (L/mol*s)
P0=10;
N=100; %degree of polimerzation
% u=[P1, P2, .... PN, W]
function dudt=deq(t,u)
P= u(1:N);
W= u(N-1);
sum3= sum(P);
sum4=0;
for ii=1:N
sum1 = 0;
for jj=1:ii-1
sum1= sum1 + P(ii-jj)*P(jj);
end % for jj
%disp([ii, P(1:2), sum1])
sum2= sum(P(ii+1:N));
dudt(ii)= k1*sum1 + 2*km1*W*sum2 - ...
2*k1*P(ii)*sum3 - km1*W*(ii-1)*P(ii);
sum4 = sum4 + (ii-1)*P(ii);
%disp([ii, sum1, sum2 sum3])
end % for ii
dudt(N+1)= k1*sum3^2 - km1*W*sum4;
dwdt(N+1)=0;
dudt=[dudt; dwdt];
end % deq
m=[0 24*3600] ;
u0=[P0 zeros(N,1) 0] ;
[t,u]=ode15(@deq,m,u0) ;
%% Plot
figure(1)
plot(t,u)
title('Time Vs. Molecular Weight')
xlabel('Time []')
ylabel('Concentration []')
end

darova on 27 Nov 2019
DId you try to change the name of a function?
function happy_girl_Project
How do you want u0 vector should looks like?
u0=[P0 zeros(N,1) 0] ;
% P0 = 10;
% zeros(N,1) - column vector
% 0 = 0
Jan on 28 Nov 2019
I've formatted the text and the code to improve the readability.

Jan on 28 Nov 2019
u0 = [P0, zeros(1, N + 1)];

#### 1 Comment

darova on 28 Nov 2019
it works