HAVE = HAD + CHANGE

dR/dt = b*R

dR = b*R*dt

R_new - R_old = b*R_old*dt

R_new = R_old + b*R_old*dt

Simple Population Model in Excel

(right click to download above or below model)

Simple Population Model in Vensim

A Short Tutorial in Vensim

A Longer Tutorial in Vensim

Simple Population Model in MATLAB Example M-File