May you guys help me I got stuck in developing a simple code... (solving diferential equations by using ode45)

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If I consider the function react2 and write the function react in the prompt command it will work!! But I want to use only the script window... Since when I'm using the prompt I first type "[t,y] = ode45('react2',[0 4],[1 0 0]);" and after that MATLAB calls the function react2 ... So I thought putting it all in a new window and executing it it would work since the first function is actually what I would've typed in the prompt... But it does not work! why?? how could I get the values for [t y] without having to type [t y ] = ode45('react2',[0 4],[1 0]) ?? HERE IS THE CODE thank you guys..
function react
[t,y] = ode45('react2',[0 4],[1 0 0]);
% =======================================
function dydx = react2(t,y)
dydx = zeros(size(y));
A = y(1); B = y(2); C = y(3);
k1 = 5 ; k2 = 2; k3 = 1;
% initial values (A0,B0,C0) = (1,0,0);
dydx(1) = -k1*A +k2*B ; dydx(2) = k1*A - (k2+k3)*B ;
dydx(3) = k3*B;

Respuesta aceptada

Star Strider
Star Strider el 9 de Mayo de 2014
It works fine as an anonymous function:
react2 = @(t, y, k1, k2, k3) [(-k1.*y(1) + k2.*y(2)); (k1*y(1) - (k2+k3)*y(2)); k3.*y(2)];
k1 = 5 ; k2 = 2; k3 = 1;
[t,y] = ode45(@(t,y) react2(t, y, k1, k2, k3),[0 4],[1 0 0]);
figure(1)
plot(t, y)
legend('A', 'B', 'C', 'Location', 'NW')
grid
  9 comentarios
Douglas Alves
Douglas Alves el 12 de Mayo de 2014
I got it. Thank you guys. dpb the way you formulated the code worked pretty well. thanks

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Más respuestas (1)

dpb
dpb el 9 de Mayo de 2014
...I thought putting it all in a new window and executing it it would work...
I don't know what you mean by the above. If you create another m-file script react.m that contains just the command line
t,y] = ode45('react2',[0 4],[1 0 0]);
and execute
react
at the command window it will work.
You don't use the function keyword in scripts is perhaps your confusion.
Read up the doc's on programming scripts and functions to clarify the difference in depth.
  2 comentarios
Douglas Alves
Douglas Alves el 9 de Mayo de 2014
I'm still testing and the way you said didnt work. But maybe I did something wrong again...
dpb
dpb el 9 de Mayo de 2014
Editada: dpb el 9 de Mayo de 2014
Need to see what you actually did, not just describe it.
ADDENDUM:
Went ahead and copied your function and created the script file--
>> type react.m
[t,y] = ode45('react2',[0 4],[1 0 0]);
>> react
>> plot(t,y)
>>
Seems to work just fine...at least a solution seems to have happened according to the plot...

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