how to get a plot of second ODE

I'm trying to solve a second order ODE and plot it, when I use rk4 method it gives me an arry of yp = NaN and this message is shown : " warning: opengl_renderer: data values greater than float capacity. (1) Scale data, or (2) Use gnuplot"

I'm not able to detect the error in the code. I tried to use ode45 it resulted in the same message.

code:

function trying

clear,clc,clf;

tspan = [0 50]; y0 = [0; 0.1];

step=0.2;

[t, y]=rk4(@f,tspan,y0,step)

plot(t,y)

end

function yp=f(t,y)

yp=zeros(2,1);

j = 6.5*10^-5;

yp(1)=y(2);

yp(2)= y(1) / (t.*j) - (y(1)/(t.^2 .*j)) - (3.*y(2)./t)

end

[Jan]

If gnuplot is suggested, this is not Matlab, but Octave. Please remember, that this is a Matlab forum.

rk4() is not a function of Matlab.

A clear on top of a function is a complete waste of time.

6.5*10^-5 is an expensive power operation, while 6.5e-5 is a cheap constant.

Answer 1

[Jan]

The interval is: tspan = [0 50]

In the first step you evaluate:

yp(2)= y(1) / (t.*j) - (y(1)/(t.^2 .*j)) - (3.*y(2)./t)

for t == 0. Then y(2) is NaN, because you divide by 0, and so are all folloing values also.

The function to be integrated is not defined on the initial time point.

[lily]

Thank you for the help.