"Not Enough Arguments" Error in ode23 - code is perfect as far as I know...

function kinetics=examquestion1(t,Y)

kinetics=zeros(3,1);

kinetics(1)=-Y(1)*Y(2)+0.1*Y(3);

kinetics(2)=-Y(1)*Y(2)+0.1*Y(3);

kinetics(3)=Y(1)*Y(2)-0.1*Y(3);

[tv,Yv]=ode45(@examquestion1,[0 10],[1;1;0],t);

plot(tv,Yv(:,1),'+',tv,Yv(:,2),'x',tv,Yv(:,3),'o')

hold on

grid

title('Solutions w/k1=1 and k-1=0.1')

text(0.3,14,'-+- A(t)')

text(0.3,10,'-x- B(t)')

text(0.3,-12,'-o- P(t)')

xlabel('time')

hold off

end

Above is my code, error is in line 4 "kinetics(1)=......." I have no clue what to do!! Please help, time is of the essence. Thank you :)

Code is for solving a system of 3 differential equations, representing the kinetics of an A + B = C reaction.

Answer 1

[Paul]

Put this in an m-file:

function kinetics=examquestion1(t,Y)

kinetics=zeros(3,1);

kinetics(1)=-Y(1)*Y(2)+0.1*Y(3);

kinetics(2)=-Y(1)*Y(2)+0.1*Y(3);

kinetics(3)=Y(1)*Y(2)-0.1*Y(3);

save it as examquestion1. Then run:

[tv,Yv]=ode45(@examquestion1,[0 10],[1;1;0]);
plot(tv,Yv(:,1),'+',tv,Yv(:,2),'x',tv,Yv(:,3),'o')
hold on
grid
title('Solutions w/k1=1 and k-1=0.1')
text(0.3,14,'-+- A(t)')
text(0.3,10,'-x- B(t)')
text(0.3,-12,'-o- P(t)')
xlabel('time')
hold off

Answer 2

[Star Strider]

You can only put a function file inside another function file. If you want your ODE to run in your file, you have to code it as an anonymous function.

You also made a simple typographical error:

[tv,Yv]=ode45(@examquestion1,[0 10],[1;1;0],t);

It will throw an error because of the t.

I reformatted your ODE as an anonymous function (for my convenience only) and this ran without problems:

examquestion1 = @(t,Y)  [-Y(1)*Y(2)+0.1*Y(3);  -Y(1)*Y(2)+0.1*Y(3);  Y(1)*Y(2)-0.1*Y(3)];
[tv,Yv]=ode45(examquestion1,[0 10],[1;1;0]);

Also, with respect to your text statements, see the legend command. It may make what you’re doing easier.