From rk-2 to rk-4

Hi, I have a problem. I have written the following code for a Runge Kutta 2 but now i want it write a code for a Runge Kutta 4. So if i'm correct i have to add a k3 and a k4 but i have no clue how. Can anyone help me?

function x = exc5rk2(k,M,h,D)
% k, m, and D are preset values
%h is the timesteps and D is the time
N = D/h;
t(1) = 0;
x(1) = 1.5;
v(1) = 0;

for i = 1:N
    t(i+1) = t(i) + h;    
    xs = x(i) + h*(v(i));
    vs = v(i) + h*(-k/M*x(i));
    x(i+1) = x(i) + h/2*(v(i)+vs);
    v(i+1) = v(i) + h/2*(-k/M*x(i)-k/M*xs);
end

plot(t,x,t,v)
return

[madhan ravi]

can't you use ode solvers?

Answer 1

[madhan ravi]

https://www.mathworks.com/help/matlab/ref/ode45.html#bu0200e-1

If you want just downloadhttps://www.mathworks.com/matlabcentral/fileexchange/29851-runge-kutta-4th-order-ode?focused=3773771&tab=function from file exchange and adapt it to your equation.