#main title ##section title ###subsection #### sub-subsection
#population growth rate can be expressed a ratio of population size
###function list ###1 female.N{2:3] # give me the second and the third year population
###2 females.N[2:3]/females.N[1:2] #give us two lambda value, one is from population number from year 1 to that from year 2 and another is from 2 to 3
###3 so if we want to calculate all the growth rate from year to year, we can do the follwing females.N[2:39]/female.N[1:38] #we are dividing the population from year(x+1) over the population from year (X)
###4 to do the same thing as the line just above we could do len<- length(female.N) females.N[2:len]/female.N[1:len-1] # this is more preferable than the method above, because it will prevent some errors if we, people, calculate the numbers like 39 or 38 wrong. Also this way is more reproducible
###5 female.Ntemp #it will show all the element
###6 female.Ntemp[-2] #it will show all the element except the second one, because we drop the second element
###7 female.Ntemp[-length(females.Ntemp)] #always drop the last element of the list in female.Ntemp
###8 female.Ntemp[-c(1:2)] #drop the first and the second element