ode45 function Not enough input arguments error.

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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
  2 Comments
Susie
Susie on 2 Oct 2013
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
Susie on 2 Oct 2013
One more thing: my line 5 is 'xdot(1) = x(2) * x(3);'

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Accepted Answer

James Tursa
James Tursa on 3 Oct 2013
Edited: James Tursa on 3 Oct 2013
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:

More Answers (2)

Azzi Abdelmalek
Azzi Abdelmalek on 2 Oct 2013
Your code is correct. Can you precise where is line 5
  4 Comments
Azzi Abdelmalek
Azzi Abdelmalek on 2 Oct 2013
Check if the right function Animate is in the current folder.
Susie
Susie on 2 Oct 2013
I have checked, it is in the current folder. :(

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Susie
Susie on 3 Oct 2013
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
  4 Comments
Joaquim
Joaquim on 22 May 2014
Edited: Joaquim on 22 May 2014
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

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