Hi, I am stuck on a point where the 's' value needs to be changed to 0.51 in the next generation (t+1) when Ns>100, otherwise it has to be default (0.5). Can you please help with this. Thanks in advance.

        e=0.98;%hatchability
        Mc=1.1;%minimum critical body mass
        delta=0.15;%adult density sensitivity
        x1=2.5;%scaling constant
        highgammayeastedHH=107;
        highF=2.8;%high larval  food
        x2=1;%scaling constant
        x3=0.009;%scaling constant
        x4=2;%scaling constant
        x5=1.7;%scaling constant
        gen=1:50;%number of generations
        Nt=20;%number of eggs laid by first females
        Adults=zeros(50,1); %pre-allocating adults
        Ns=zeros(50,1);Ns(1)=Nt;
        Nt=20;%number of eggs for first generation
        s =.51;

        for t=1:20%iterating the loop
            Nl=floor(e*Nt);%number of larvae survived
            if Nl==0
                Nl=8;%condition for extinction, when a pop goes extinct, I start it with 15 larvae
            end
            mean=x1*(1-(1/(x2+exp(-x3*Nl+highF))));%mean (body weight)
            L=normrnd(mean,0.45,[1 Nl]);%randomly extracting Nl individuals from a normal distribution
            Na=L(L>=Mc);%picking individuals with body weight greater or equal to minimum critical weight
            Ns=numel(Na);%summing the number of individuals who crossed the critical weight

            if  Adults>=100
               R=binornd(Ns,s,1);
            else
               R=binornd(Ns,.5,1);

            end
            fem=randsample(Na,R);%number of females
            Fem=numel(fem);
            Ssi=log(x4+x5*(fem));%allocating some propotion of body wieght to fecundity
            NA=Ns;%adult density realized by each individual
            G=1/(1+delta*NA);%effect of adult density on fecundity
            ni=highgammayeastedHH*Ssi*G;%fecundity of an ith individual
            Nt=sum(ni);%summing the number of eggs laid by females
            N(t)=Nt;%number of eggs for the next generation
            Adults(t)=Ns;%adults

end

Answer 1

[Geoff Hayes]

Neha - since Ns is defined to be

 Ns=numel(Na);

then why not do something similar to what you have already

 if  Ns >= 100
     s = 0.51;
 else
     s = 0.5;
 end
 R=binornd(Ns,s,1);

Try implementing the above and see what happens!

[neha p]

Hi Hayes,

Thanks for your reply but this will affect the sex ratio in that generation itself. It will not affect the sex ratio in the following generation, will it? I want sex ratio to change only if the previous generation had more than 100 individuals, otherwise it has to be 50 percent. I don't know how can i execute this for the next generation.

[Geoff Hayes]

If you don't want this to affect the current iteration, then put this code

 if  Ns >= 100
     s = 0.51;
 else
     s = 0.5;
 end

at the end of the loop (so that is the last thing to execute before the next iteration begins).