Whats wrong with these scripts? I can't get them to work.

Question

Adam Goza 2016-3-20

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/274585-whats-wrong-with-these-scripts-i-can-t-get-them-to-work

评论： Adam Goza 2016-3-21

Script:

[W,y] = ode45(@eqtP426,[0 368],[2; 2; 0; 0]);
plot(W,y(:,1),'-',W,y(:,2),'--',W,y(:,3),'-*',W,y(:,4),'-')
title('Solution of P4-26');
xlabel('Catalyst weight W');
ylabel('Solution y');
legend('y_1','y_2','y_3','y_4')

Script:

function dydW = eqtP426(W,y)
CT0 = 0.4
FT0 = 4
kh = 0.1
keq = 1.44
k = 1.37
dydW =[-(k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq); 
    -(k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq);
    (k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq);
    (k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq)- 
     kh*CT0*y(4)/(y(1)+y(2)+y(3)+y(4))]

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Answer 1

Geoff Hayes 2016-3-21

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/274585-whats-wrong-with-these-scripts-i-can-t-get-them-to-work#answer_214378

在 MATLAB Online 中打开

Adam - when I run your code, I observe the following error

Error using feval
Error: File: eqtP426.m Line: 10 Column: 69
Expression or statement is incorrect--possibly unbalanced (, {, or [.
Error in odearguments (line 87)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.
Error in ode45 (line 113)
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn,
...

This is due to how you initialize dydW in eqtP426.m

dydW =[-(k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq); 
       -(k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq); 
       (k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq);
       (k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq)- 
        kh*CT0*y(4)/(y(1)+y(2)+y(3)+y(4))]

The fourth element of the above array requires the long line continuation using an ellipsis as

dydW =[-(k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq); 
       -(k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq); 
       (k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq);
       (k*CT0^2/(y(1)+y(2)+y(3)+y(4))^2)*(y(1)*y(2)-y(3)*y(4)/keq)- ...
        kh*CT0*y(4)/(y(1)+y(2)+y(3)+y(4))];

Try making the above change and re-run your code.