%LPA.m - this MATLAB file solves the 
%discrete Larva-Pupa-Adult model of flour beetles.

b=11.677;
Ul=0.5129;
Cea=0.011;
Cel=0.0093;
Cpa=0.0178;
Ua=0.11; %input('input adult mortality Ua:    ')
L0=70;  %input('input initial population L0:     ')
P0=30;
A0=65;
n=40;  %input('end of time interval b:     ')
L=zeros(n+1,1);
P=zeros(n+1,1);
A=zeros(n+1,1);
t=zeros(n+1,1);
L(1)=L0;
P(1)=P0;
A(1)=A0;
for i=1:n
t(i)=i-1;
L(i+1)=b*A(i)*exp(-Cea*A(i)-Cel*L(i));
P(i+1)=L(i)*(1-Ul);
A(i+1)=P(i)*exp(-Cpa*A(i))+A(i)*(1-Ua);
end
t(n+1)=n;
plot(t,L,'-o',t,P,'r:.',t,A,'-*')
legend('Larvae','Pupae','Adults',0)