Hello, I'm having some trouble with my octave coding and would appreciate any input on where the issue lies. The coding is as follows: Code (Matlab M): age = [0:1:100]; %this is the age matrix, represented by a time = [0:1:100]; %this is the time matrix, represented by t population = zeros(101,101); for a = 1:101; population(a,1) = 0.5; %this is the initial population B(a) = (1./(2.*a)); %this is the birthing probability at age (a) endfor for t = 1:100 for a = 2:101 population(1,t+1) = cumtrapz(B(a)); %this is the birth rate population(a,t+1) = population(a-1,t); %this is the interation process endfor endfor surf(age,time,population) <Moderator's note: code tags added. Please use them when posting code.> The issue I'm having lies in the population matrix computation; the cumtrapz integration is not recognizing the step process and all outputs from t = 2:101 in the population matrix are zeros. I would again appreciate any help to understand where the issue lies. Thank You, Jacob M.