runge-Kutta problem command ode45

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评论： Star Strider 2021-3-1

I try to solve an equation with the command ode45 b ut I have an error, this is my code:

tspan = [0 5];

y0 = 100;

Q = 30, b = 0.2;

[t,y,x] = ode45(@(tspan,y,x) Q-b*x*y, t, y0);

plot (t,y,x,'-o')

and the error:

Q =

Not enough input arguments.

Error in rungrkutta_y>@(tspan,y,x)Q-b*x*y (line 4)

[t,y,x] = ode45(@(tspan,y,x) Q-b*x*y, t, y0);

Error in odearguments (line 90)

f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ode45 (line 115)

odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in rungrkutta_y (line 4)

[t,y,x] = ode45(@(tspan,y,x) Q-b*x*y, t, y0);

how can I solve it?

Star Strider 2021-3-1

I have no idea what you want to do, or what ‘x’ and ‘y’ are.

This will get you closer to an actual result:

tspan = [0 5];
y0 = [100; 0];
Q = 30; 
b = 0.2;
[t,y] = ode45(@(t,y) [y(1); Q-b*y(1)*y(2)], tspan, y0); 
figure
plot (t,y,'-o')

I think that it will work, thank you!

Star Strider 2021-3-1

As always, my pleasure!

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