with(DEtools);fv := v*(0.3-v)*(v-1.0); sgma := 0.0;for isigma from 1 to 2 do
if(isigma = 1) then sgma := 0.0 fi;
if(isigma = 2) then sgma := -0.5 fi;
f1 := w; f2 := -sgma*w - fv;
A := linalg[jacobian]([f1,f2],[v,w]);
A0 := map(aij->subs(v=0,w=0,aij),A);
evsystem0 := linalg[eigenvectors](A0);
pos_evecs0 := evsystem0[1]:
if(pos_evecs0[1]<0) then pos_evecs0 := evsystem0[2] fi;
pos_evecs0;
evec0plus := pos_evecs0[3][1];
A1 := map(aij->subs(v=1,w=0,aij),A);
evsystem1 := linalg[eigenvectors](A1);
neg_evecs1 := evsystem1[2]:
if(neg_evecs1[1]>0) then neg_evecs1 := evsystem1[1] fi;
neg_evecs1;
evec1minus := neg_evecs1[3][1];
phaseportrait([diff(v(t),t)=w(t), diff(w(t),t) = subs(v=v(t),w=w(t),f2)],
[v(t),w(t)],t=-20..20,[[v(0)=0.001*evec0plus[1],w(0)=0.001*evec0plus[2]],
[v(0)=-0.001*evec0plus[1],w(0)=-0.001*evec0plus[2]],
[v(0)=1.0+0.001*evec1minus[1],w(0)=0.001*evec1minus[2]],
[v(0)=1.0-0.001*evec1minus[1],w(0)=-0.001*evec1minus[2]]
],v=-0.2..1.2,w=-0.4..0.4,stepsize=0.01);
od;neg_evecs1[1];