function [] = population (y10,y20,time)

% solve the system y1'=by1-cy1y2; y2'=-dy2+cy1y2; 
% plot populations y1(t) and y2(t);
% plot trajectory of point (y1(t),y2(t)) in the plane as a function of time

options = odeset('RelTol',1e-4,'AbsTol',[1e-5 1e-5]);
[T,Y] = ode45('lotka_volt',[0 time],[y10 y20],options);
figure(1);
plot(T,Y(:,1),'-',T,Y(:,2),'.')
title('y1 ---  y2 ... ')
figure(2);
plot(Y(:,1),Y(:,2),'.')
title('Phase plot (y1,y2)')


%COMPUTER PROBLEM 9.1
%Physical interpretation of the behaviour
%Find nonzero population where one of populations disapeare?.