#===========================================================
# Figure 10.6.R.
# R script to plot the logistic model of population growth.
#===========================================================
k=100      # Population levels off at k.
b=.5       # Higher value of b will result in quicker approach to k.
m=5        # Initial population size is m.
t=(0:100)*20/100  # Range of values of time t from 0 to 20.
n=k/(1+((k-m)/m)*exp(-b*t))  # Logistic population growth function.
plot(t,n,type="l",xlab="time",ylab="population size")  # Plot n vs t.
k.level=numeric(length(t))+k;      # Vector with elements all equal to k.
points(t,k.level,type="l",lty=2)   # Add dashed line at the level of k.