#=========================================================
# Figure 11.1.R.
# R script to calculate and plot age class sizes through
# time for an age-structured wildlife population, using 
# the matrix projection model.  Demographic rates for the
# Northern Spotted Owl are from Noon and Biles
# (Journal of Wildlife Management, 1990).
#=========================================================
num.times=20
num.ages=3

p1=.11  # Age-specific survival and fecundity rates.
p2=.71  #
p3=.94  #
f=.24   #

M=rbind(c(0,0,f),c(p1,0,0),c(0,p2,p3))  # Projection matrix.

N=matrix(0,num.times,num.ages) # num.times X num.ages matrix of 0’s.
                               #  Rows of N will be the population
                               #  vectors through time.

N[1,]=c(1200,800,2000)  # First row of N contains initial sizes.

for (t in 1:(num.times-1)) {
   N[t+1,]=M%*%N[t,]
}
N    # Print N to the console.

time.t=0:(num.times-1)
#------------------------------------------------------------
# Following matplot() function plots every column of N (vertical
# axis) versus time.t (horizontal axis) & accepts all graphical
# arguments of the plot() function.
#------------------------------------------------------------
matplot(time.t,N,type="l",lty=c("dashed","longdash","solid"),
  xlab="time in years",ylab="population size",
  ylim=c(0,2600),col="black")