ode45 function Not enough input arguments error.

Hello,

I copied a simple tutorial online on how to use an ode45 function. I have checked and double checked everything. I am going insane :) Any help would be greatly appreciated. I continuously receive the error:

*NOTE: I am a novice at MATLAB

 if true
>> Animate
Error using Animate (line 5)
Not enough input arguments.
  end

Here is my code:

if true
  function xdot = Animate(t,x)
  xdot = zeros(3,1); 
  xdot(1) = x(2) * x(3);
  xdot(2) = -x(1) * x(3);
  xdot(3) = -0.51 * x(1) * x(2);

[t,x] = ode45('Animate',[0 12], [0 1 1], options);
plot(t,x(:,1), '-',t,x(:,2),'-.',t,x(:,3),'.')
end

[Susie]

By the way, the 'if true' and 'end' statements at the beginning and end of my code are just part of the way this comment box formatted my code. Couldn't get rid of them. Those lines are not in my actual MATLAB code.

Thanks

[Susie]

One more thing: my line 5 is 'xdot(1) = x(2) * x(3);'

Answer 1

[James Tursa]

FYI the doc says 1st argument to ode45 is supposed to be a function handle, not a string (although a string also seems to work). Try this:

[t,x] = ode45(@Animate,[0 12], [0 1 1], options);
plot(t,x(:,1), '-',t,x(:,2),'-.',t,x(:,3),'.')

It looks like the error you are getting is because you are typing in Animate without any arguments.

In any event, I get this plot by typing in the above two lines with your Animate.m function:

[Azzi Abdelmalek]

ode45('Animate',[0 12], [0 1 1], options);

also works

Answer 2

[Azzi Abdelmalek]

Your code is correct. Can you precise where is line 5

[Susie]

My line 5 is xdot(1) = x(2) * x(3);

[Susie]

I have no idea what I am doing wrong. I keep receiving that error message.

[Azzi Abdelmalek]

Check if the right function Animate is in the current folder.

[Susie]

I have checked, it is in the current folder. :(

Answer 3

[Susie]

James,

I made that change, but still had the same error. So, I created an x row vector x = [1 5 10]. I'm getting different errors now. Can you post your changes because I'm not getting a plot at all.

Thanks

if true
  function xdot = Animate(t,x)
  xdot = zeros(3,1);
  x = [1 5 10]
  xdot(1) = x(2) * x(3);
  xdot(2) = -x(1) * x(3);
  xdot(3) = -0.51 * x(1) * x(2);

   [t,x] = ode45(@Animate,[0 12], [0 1 1]);
    plot(t,x(:,1), '-',t,x(:,2),'-.',t,x(:,3),'.')
  end

[James Tursa]

I have a file called Animate.m in my current directory, which is:

function xdot = Animate(t,x)
xdot = zeros(3,1); 
xdot(1) = x(2) * x(3);
xdot(2) = -x(1) * x(3);
xdot(3) = -0.51 * x(1) * x(2);
end

I then type in the following two lines at the command line (your options variable deleted from the call since you didn't specify what it was) and I get the plot:

[t,x] = ode45('Animate',[0 12], [0 1 1]);
plot(t,x(:,1), '-',t,x(:,2),'-.',t,x(:,3),'.')

[Susie]

<3333333333 !!!!!!!!!!!!!!!!!!!!!!!!!!!!

Thank you!

[Joaquim]

Hi, I had the same problem when i put >> [Ti,Yi]=solver(ode1,tspan,y0), after defining tspan and y0 in the command prompt.

Anyone can help me? I send the file attached. Thank you

[Joaquim]

here it is