Attempting to solve a differential with inital conditions and a time range and then plot the function and it's derivative on a graph and to determine the time when the function first crosses zero.
x0 = [20;0]; %Inital conditions
tr = [0; 300]; %Time range for our function
[t,y]=ode45(@fun, tr, x0);
Pi=find(t<0); %Find elements of Z less than 0
Pi1=Pi(1); % the array index for first Z element<0
zz=Z(Pi1-4:Pi1+3); %Pick 8 elements from Z
tt=t(Pi1-4:Pi1+3); %Pick 8 elements from t
% (tt, zz) will be used for interpretation
plot(t,y)
plot(tt,zz)
function dydx = fun(t,x)
%dx(1)/dt = dy/dt = x(2)
%dx(2)/dt = d^2y/dt^2
dydx = [x(2);
0.375*sign(x(2))*(x(2))^2+0.00074*x(1)];
end
The error I get is shown below. If anyone can help that'd be great
Warning: Failure at t=2.082134e+01. Unable to meet
integration tolerances without reducing the step size below
the smallest value allowed (5.684342e-14) at time t.
> In ode45 (line 360)
In ME2602Ahmed_P4_1 (line 4)
Index exceeds the number of array elements (0).
Error in ME2602Ahmed_P4_1 (line 7)
Pi1=Pi(1); % the array index for first Z element<0
