Input argument "x" is undefined.

How do I correct undefined input argument x?

Error:

??? Input argument "x" is undefined.

Error in ==> ckt at 7

xdot(1) = x(2)/C1;

Code:

function xdot = ckt(t,x)

vg=1;

C1=100e-9;

C2=100e-9;

R=30;

L=184e-6;

xdot(1) = x(2)/C1;

xdot(2) =-(x(1) + x(3))/L + vg/L;

xdot(3) = x(2)/C2 - x(3)/(R*C2);

xdot = [xdot(1); xdot(2); xdot(3)];

t0=0; tf=60e-6;

tspan=[t0,tf];

x0=[-1 0 0]' ;

[t,x]=ode45('ckt',tspan,x0);

plot(t,x(:,3))

Answer 1

[Star Strider]

Instead of using the single quotes, call the function in ode45 with a function handle as:

[t,x]=ode45(@ckt,tspan,x0);

so the full code is now:

   t0=0; tf=60e-6;
   tspan=[t0,tf];
   x0=[-1 0 0]' ;
   [t,x]=ode45(@ckt,tspan,x0);
   
   figure
   plot(t,x(:,3))

function xdot = ckt(t,x)
   vg=1;
   C1=100e-9;
   C2=100e-9;
   R=30;
   L=184e-6;
   xdot(1) = x(2)/C1;
   xdot(2) =-(x(1) + x(3))/L + vg/L;
   xdot(3) = x(2)/C2 - x(3)/(R*C2);
   xdot = [xdot(1); xdot(2); xdot(3)];
   t0=0; tf=60e-6;
end

And it works correctly.

See the documentation on What Is a Function Handle? for details.

[Hani Daniel]

Thank you very much for your help.

Hani Daniel

[Star Strider]

As always, my pleasure!