How can I create a subplot of ode45 for a mass spring damper where the two plots have a different k value?

I'm new to MATLAB and i'm trying to create two subplots side by side, where the only difference is the 'k' value in the mass spring damper equation is different.

Here is the code:

function zprime= msdfunc(t,z)
m = 4; b = 0.25; k = 2;
zprime=[z(2);-(b/m)*z(2)-(k/m)*z(1);];
end

tspan=[0, 60];
y0=[0, 4];
[t, y]=ode45(@msdfunc, tspan, y0);
plot(t, y);

I need to plot the equation for k=2 and k=4.

Thanks in advance

Answer 1

[Bjorn Gustavsson]

Simply add another parameter to your msdfunc for k:

function zprime= msdfunc(t,z,k)
m = 4; b = 0.25;
if nargin < 2 || isempty(k)
  k = 2; % Your default value
end
zprime=[z(2);-(b/m)*z(2)-(k/m)*z(1);];
end

Then you can solve the ODE for different values of k:

[t_k4, y_k4]=ode45(@(t,y) msdfunc(t,y,4), tspan, y0);

Then you can plot away in any organization of subplots.

HTH