Matlab Help Input argument undefined

[matlabphd]

Dear all. I am trying to solve an ODE in MATLAB using ODE45 solver. But the programe keep saying

? Input argument "y" is undefined.

Error in ==> lvv at 4
yprime=[a*y(1)-b*y(1)*y(2);-r*y(2)+c*y(1)*y(2)];

Can anybody be of help? Please.

The complete code is this:
function yprime=lvv(t,y)
%LV: Contains Lotka-Volterra equations
a=.5471;b=.0281;c=.0266;r=.8439;
yprime=[a*y(1)-b*y(1)*y(2);-r*y(2)+c*y(1)*y(2)];
[t,y]=ode45(@lvv,[0 20],[30;4])
plot(t,y(:,1))
Thanks

 

[CEL]

Dear all. I am trying to solve an ODE in MATLAB using ODE45 solver. But the programe keep saying

? Input argument "y" is undefined.

Error in ==> lvv at 4
yprime=[a*y(1)-b*y(1)*y(2);-r*y(2)+c*y(1)*y(2)];

Can anybody be of help? Please.

The complete code is this:
function yprime=lvv(t,y)
%LV: Contains Lotka-Volterra equations
a=.5471;b=.0281;c=.0266;r=.8439;
yprime=[a*y(1)-b*y(1)*y(2);-r*y(2)+c*y(1)*y(2)];
[t,y]=ode45(@lvv,[0 20],[30;4])
plot(t,y(:,1))
Thanks

When you call the function do you provide the matrices t and y? If not, the function does not know what y is.

 

[oswaler]

for reaching out for help with your ODE problem in MATLAB. It seems like the issue lies in the definition of your input arguments for the ODE solver. The error message suggests that the variable "y" is not being properly defined in your code. Have you declared "y" as a variable before using it in the function "lvv"? Additionally, make sure that the input arguments for the ODE solver match the function you are using (@lvv in this case). I recommend double-checking your code and making sure all variables are properly defined before running the program again. If the issue persists, please provide more information about your code so that I can further assist you. Best of luck with your ODE solving!