Not enough input arguments. in ode45

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minu pilvankar
minu pilvankar 2019-8-29
评论： Steve 2020-3-25
Hi,
I am trying to run the code given as an example on mathworks website (https://www.mathworks.com/help/matlab/ref/ode45.html) for ode45 and still it is giving me the error saying : "Not enough input arguments"
This is the code:
function dydt = vdp1(m,y)
dydt = [y(2); (1-y(1)^2)*y(2)-y(1)];
[m,y] = ode45(@vdp1,[0 20],[2; 0]);
plot(m,y(:,1),'-o',m,y(:,2),'-o')
title('Solution of van der Pol Equation (\mu = 1) with ODE45');
xlabel('Time t');
ylabel('Solution y');
legend('y_1','y_2')
I am trying this as I am developing a new code based on this template and that is not working either.
What can I do?
  4 个评论
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Star Strider
Star Strider 2019-8-29
I changed it only to use the anonymous function version of ‘vdp1’ (and the appropriate reference to it in the ode45 call) and it ran without error:
vdp1 = @(m,y) [y(2); (1-y(1)^2)*y(2)-y(1)];
[m,y] = ode45(vdp1,[0 20],[2; 0]);
plot(m,y(:,1),'-o',m,y(:,2),'-o')
title('Solution of van der Pol Equation (\mu = 1) with ODE45');
xlabel('Time t');
ylabel('Solution y');
legend('y_1','y_2')
The first argument to a function the ODE solvers use is the dependent variable (usually ‘t’, here ‘m’), and the second is the dependent variable, here ‘y’. The code is correct and runs without error.
We are not seeing the code that is throwing the error, so it is not possible to figure out what the problem is.
Steve
Steve 2020-3-25
Thank you--the 2nd version given by Star Strider does work on my machine. However, the 1st version does not. I believe it has to do with the name my program is stored under.
I apparently need to study the instructions for using handles.

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采纳的回答

madhan ravi
madhan ravi 2019-8-29
[m,y] = ode45(@vdp1,[0 20],[2; 0]);
plot(m,y(:,1),'-o',m,y(:,2),'-o')
title('Solution of van der Pol Equation (\mu = 1) with ODE45');
xlabel('Time t');
ylabel('Solution y');
legend('y_1','y_2')
% try the above in command window or in a separate script file
% ------------
function dydt = vdp1(m,y) % save this in a separate file named as vdp1.m
dydt = ...;
  2 个评论
minu pilvankar
minu pilvankar 2019-8-29
Thanks for the response! Yeah, thats what I thought coz it ran fine on my lab computer. Not sure what is wrong then.

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