Genetic Algorithm

I want to know how rank selection work in detail.

And I have also read this linear function for rank selection.
   
     prob(rank) = q - (rank -1)^r

where q = a user defined parameter ( q varies between 1/pop_size and
2/pop_size)

This function returns the probability of an individual ranked in
position rank
(rank = 1 means the best individual, rank = pop_size the worst one) to
be selected.

e.g; pop_size=100 and q=0.015 then r=q/(pop_size-1) =0.00015151515

and prob(1)=0.015
    prob(2)=0.0148484848
    :
    prob(100)=0.00000000000000000051

    I have got these probabilities and how can I use these
probabilities to select chromosomes.
    I also want to use this rank selection method in Evolutionary
Planner/Navigator. Please suggest me.

Thanks in advance.

With Regards,
May