%
%discretepredprey.m - this MATLAB file solves the 
%discrete non-linear host-parasitoid system
% x(i+1)=R0*x(i)/(1+y(i))
% y(i+1)=x(i)*y(i)/(1+y(i))
% and the user is prompted to read in the value
% of R0 to use as well as the initial value
% x0 and y0 and the time interval over which to run the 
% simulation.
s=1;
while s>0;
R0=input('input parameter R0:    ')
x0=input('input initial population x0:     ')
y0=input('input initial population y0:     ')
n=input('end of time interval b:     ')
x=zeros(n+1,1);
y=zeros(n+1,1);
t=zeros(n+1,1);
x(1)=x0;
y(1)=y0;
for i=1:n
t(i)=i-1;
x(i+1)=R0*x(i)/(1+y(i));
y(i+1)=x(i)*y(i)/(1+y(i));
end
t(n+1)=n;
plot(t,x,t,y,'o'),pause
figure
plot(x,y,'x'),pause
s=input('Do you want to stop - if so enter 0')
end
