matlab 'Index exceeds array boundaries'

by this code, that error happens...and i dunno why...

function H12 =H1(t,X)

m=10;

c=1000;

k=100000;

e=0.001;

w=100;

R=0.5;

X=R*cos(w*t);

Y=R*sin(w*t);

F1=m*e*w^2*cos(w*t);

F2=m*e*w^2*sin(w*t);

H12=[X(2); -c/m*X(2)-k/m*X(1)+F1/m];

end

--------------------------------------------------------

t=0:0.1:20;

X0=[0,0];

>>

[t,X]=ode45(@H1,t,X0);

[madhan ravi]

What’s X(2) ? Will you post the latex form of the equation?

[alsgud qor]

It s a second derivate form...um..I think I misunderstood that matlab automatically understood that thing...also X(1) is equal to X's first derivate..I put

X(1)=diff(X);

X(2)=diff(X(1));

in that function and it s still ain't working...

Answer 1

[Devineni Aslesha]

In the given code, the initial conditions are passed to 'ode45' from the variable 'X0' which is a vector. The 'X0' values are taken by the variable 'X' to obtain the ode solver output. However, in the code, the variable 'X' is modified in such a way that it becomes a scalar value due to which the error occurs. The error can be resolved by not modifying the variable 'X' in the function definition.

I would like to know why the variable 'X' has to be modified in the function definition.