MATLAB: Function Error

error

When I input my very simple code, i get this:
 function dx = lotka_volterra(t, x)
    dx = [0; 0];
    alpha = 1;
    beta = .05;
    delta = .02;
    gamma = .5;
    dx(1) = alpha * x(1) - beta * x(1) * x(2);
    dx(2) = delta * x(1) * x(2) - gamma * x(2);
    options = odeset('RelTol', 1e-4, 'NonNegative', [1 2]);
    [t,x] = ode45('lotka_volterra', [0 20], [10 10], options);
    plot(t,x);
??? function dx = lotka_volterra(t, x)
    |
Error: Function definitions are not permitted in this context.
Not sure what this means, and I read other posts, but they were not helpful.

Best Answer

You must store that code in a file named lotka_volterra.m
You cannot enter a function at the command prompt, or inside a script.
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