rm(list=ls())

p=.75; #fraction of cells that survive each reproduction
generation_end=100;  #predict up to this generation in the future
K=2000;   #reproduction capacity

#Define list (vector) nvector, where nvector(t) is number of cells per generation
#Dummy list -- all zeros
nvector=rep(0,generation_end);

nvector[1] = 1000; #initial number of cells (generation 0)

for (t in 2:generation_end)
  nvector[t] <- 4*nvector[t-1]*p*(1 - nvector[t-1]/K)

# way 1
vector_of_times_over_limit <- vector()
for (t in 1:generation_end)
  if (nvector[t] > 30)
    vector_of_times_over_limit <- c(vector_of_times_over_limit, t)

# way 2
vector_of_times_over_limit <- which(nvector[t] > 30)

# plot!
tvector=1:generation_end;

plot(tvector, nvector, pch = 1, cex = 1, type = "b",
     main = "My First Plot in R", xlab = "t", ylab = "N(t)")