I wish to calculate the number of objects in the population I'm selecting from, given that I am choosing r objects and there are nCr different combinations.
I wish to calculate the number of objects in the population I'm selecting from, given that I am choosing r objects and there are nCr different combinations.
Do you know the equation for [itex]_{n}C_{r}[/itex]?
You can do it for reasonable values of C and r but there is no simple formula- it is really a matter of factoring as you can the specific value of C. And, of course, it is important that C actually be a binomial coefficient. The great majority of integers are NOT.
It can be done by a simple search starting at n=r and using (n+1)Cr = nCr*(n+1)/(n+1-r). Since the terms are increasing it is guaranteed to find a solution if it exists.
