How to draw phase portrait

i have a set of eight equations given by the function,

function dx=agestructure(t,x)
dx=zeros(8,1);
dx(1)=912-0.0000905*x(1)*x(8)-0.00004*x(1)-0.00000986*x(1)+0.0027*x(3);
dx(2) = 608+0.00000905*x(1)*x(8)-0.00004*x(2)-0.0014*x(2);
dx(3)= 0.0014*x(2)-0.00004*x(3)-0.00000986*x(3)-0.0027*x(3);
dx(4)= 505.49+0.00000986*x(1)-0.00000905*x(4)*x(8)-0.00004*x(4)+0.0027*x(6);
dx(5)= .506+0.00000905*x(4)*x(8)-0.00004*x(5)-0.0035*x(5);
dx(6) = 0.0035*x(5)-0.00004*x(6)+0.00000986*x(3)-0.0027*x(6);
dx(7)=  500-0.000041665*x(7)*(x(2)+x(5))-0.05*x(7);
dx(8)=0.000041665*x(7)*(x(2)+x(5))-0.05*x(8);
end

I am able to draw the phase portrait using the following commands:

options=odeset('OutputFcn',@odephas2);
[t,xa]=ode45(@(t,x)g(t,x),[0 300],[3500,0,0,6500,0,0,1000,550],options);

Is it possible for me to show the vector field and path of the trjectory using 'quiver'?

[Avinash]

can u please send a working code like what values you have defined to x(1) and others

Answer 1

[KSSV]

plot(t,xa(:,1)) 

In the baove use your required index for the column and plot. You can use quiver, if you have vectors. Assuming your fixt column is displacement, you can plot phase potrait using:

s = xa(:,1) ;  
plot(s,gradient(s))