//  Volterra avec Euler explicite
//
//
a=1;b=1;c=1;d=1;y01=3;y02=0.5;
deff('ydot=fvol(t,y)','ydot=[a*y(1)-b*y(1)*y(2);-c*y(2)+d*y(1)*y(2)]')
//
T=100;
N=20000;
h=T/N;
t=0:h:T;
//
y=[y01;y02];
//
Yapp=[y];
for i=1:N
 y=y+h*fvol(t(i),y);
 Yapp=[Yapp,y]
end
figure(1)
clf()
plot(t,Yapp(1,:),'b-');
plot(t,Yapp(2,:),'black-');
//
figure(2);
clf()
plot(Yapp(1,:),Yapp(2,:))
