#Project sizes of population growing at finite rate R = 1 +r
#By R. Gomulkiewicz


initial.size <- 100 #starting populatio size

r <- 0.01 #intrinsic rate of increase

#next.size <- initial.size*(1+r)

#create a list to hold all the population sizes at all the steps
steps <- 10
next.size <- matrix(0, steps+1, 1)

#store the initial population size
next.size[1,1] <- initial.size

#this is a function that computes the population size at the next time step
next.size.function <- function(n, r) {n*(1+r)}

#this is a "loop" that projects the population sizes at all steps
for(i in 1:steps){ next.size[i+1,1] <- next.size.function(next.size[i,1],r) }

#plot the results
plot(-5:5,next.size,xlab="steps",ylab="population size",type="b")