ode45 function Not enough input arguments error.

Question

Susie 2013-10-2

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/88978-ode45-function-not-enough-input-arguments-error

编辑： Joaquim 2014-5-22

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

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Susie 2013-10-2

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 2013-10-2

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

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Answer 1

James Tursa 2013-10-3

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/88978-ode45-function-not-enough-input-arguments-error#answer_98530

编辑：James Tursa 2013-10-3

在 MATLAB Online 中打开

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:

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Azzi Abdelmalek 2013-10-3

在 MATLAB Online 中打开

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

also works

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Answer 2

Azzi Abdelmalek 2013-10-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/88978-ode45-function-not-enough-input-arguments-error#answer_98522

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

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Azzi Abdelmalek 2013-10-2

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

Susie 2013-10-2

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

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Answer 3

Susie 2013-10-3

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/88978-ode45-function-not-enough-input-arguments-error#answer_98533

在 MATLAB Online 中打开

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