I am trying to write this function for ode. But it always gives me an error as not enough input arguments. Here is my code associated:

I am trying to write this function for ode. But it always gives me an error as not enough input arguments. Here is my code associated:

function dxdt = odefcn(x,a) 
dxdt = zeros(3,1); 
dxdt(1) = x(2); 
dxdt(2) = x(3); 
dxdt(3) =-a*x(3)+x(2)-x(1);
 end

Answer 1

[Walter Roberson]

Do not use

   ode45( odefcn, .....)

Use

ode45( @odefcn, .....)

[Sam17]

Actually i am writing this as a function for my ODE. But this function doesn't run. It always give the same error as not enough input arguments.

Here's my main code:

a=2
tspan = [0 5];
[t,x] = ode45(@(t,x) odefcn(t,x,a), tspan, 0);
figure;
plot(t,x);
grid on;

[Walter Roberson]

With that code you should be getting an error about too many input arguments, not about not enough input arguments.

You should be using

[t,x] = ode45(@(t,x) odefcn(x,a), tspan, 0);

[Sam17]

I did tried the similar code line which you have written here. Still, my error is same. "Error using odefcn (line 3) Not enough input arguments." I dont know what's wrong with my line 3.

[Walter Roberson]

a=2
tspan = [0 5];
X0 = ones(1,3);
[t,x] = ode45(@(t,x) odefcn(x,a), tspan, X0);
figure;
plot(t,x);
grid on;

with

function dxdt = odefcn(x,a) 
dxdt = zeros(3,1); 
dxdt(1) = x(2); 
dxdt(2) = x(3); 
dxdt(3) =-a*x(3)+x(2)-x(1);
end

[Sam17]

Thankyou for your help. I did solve it.