function xd=linear725(t,x) xd(1)=(x(2)); //x(dot); x(2) means y. xd(2)=-x(1)-x(2)+x(1)^2+x(2)^2; //y(dot); x(1) means x.; endfunction bound=[-15,-15,15,15]; //Bounds of x-axis and y-axis as [xmin ymin xmax ymax], change them according to your needs. nrect=22; //increase it to get more number of curves, i.e. more information will be available. set(gca(),"auto_clear","off") //hold on x=linspace(bound(1),bound(3),nrect); y=linspace(bound(2),bound(4),nrect); x0=[]; for i=1:22 x0=[x(i);y(i)]; t0=0; t=0:0.01:6000; xout=ode(x0,t0,t,linear725); plot2d(xout(1,:),xout(2,:)); end xtitle('Phase Portrait','x-axis ( x )','y-axis ( y )')