Problem with ode solvers

I'm trying to use ode45 to solve a system of ODE, but it returns my initial conditions, what I did wrong?

function dy = camila(t,y)

dy = zeros(4,1); dy(1) = -0.5*dy(4)-0.5*dy(3)-0.5*y(4); dy(2) = -0.5*dy(4); dy(3) = 0.5*dy(1); dy(4) =5*((5/(5+2))*(1-((y(2)/y(1))/3)^2))*y(4);

[T, XY] ode45('camila',0,10,[36.128 0.505 0.54 0])

T =

         0
    0.2500
    0.5000
    0.7500
    1.0000
    1.2500
    1.5000
    1.7500
    2.0000
    2.2500
    2.5000
    2.7500
    3.0000
    3.2500
    3.5000
    3.7500
    4.0000
    4.2500
    4.5000
    4.7500
    5.0000
    5.2500
    5.5000
    5.7500
    6.0000
    6.2500
    6.5000
    6.7500
    7.0000
    7.2500
    7.5000
    7.7500
    8.0000
    8.2500
    8.5000
    8.7500
    9.0000
    9.2500
    9.5000
    9.7500
   10.0000

DY =

   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0
   36.1280    0.5050    0.5400         0

Answer 1

[Star Strider]

You have a minor problem with the way you specify the integration time interval.

From the documentation (with added emphasis):

[T,Y] = solver(odefun,tspan,y0)

‘ tspan --- A vector specifying the interval of integration, [t0,tf]. ’

I did not run your code, but if you change your call to ode45 to:

[T, XY] ode45('camila',[0,10],[36.128 0.505 0.54 0])

It should work as you want it to if you did everything else correctly.

[Pedro]

didn't work, give me the same initial condition

[Star Strider]

Something is wrong with your differential equation. You are mixing ‘y’ and ‘dy’, and the ode solvers want one or the other on the right side of the equations.

What are the original equations you want to integrate?