creating a random combination


by reldridge
Tags: combination, creating, random
reldridge
reldridge is offline
#1
Dec3-12, 02:10 PM
P: 5
I am creating a random combination(code) for a client. I need to see what the total number of combinations there can be.

Please let me know if I am using the wrong word Combination vs Permutations.

Formula:
2 letters + 2 numbers + 2 letters
example: TR12FR

The random letters are taken from 24 values:
ABCDEFGHJKLMNPQRSTUVWXYZ

The random Numbers are taken from 8 Values:
23456789

Any help would be greatly appreciated.

Thanks
Ryan.
Phys.Org News Partner Mathematics news on Phys.org
Researchers help Boston Marathon organizers plan for 2014 race
'Math detective' analyzes odds for suspicious lottery wins
Pseudo-mathematics and financial charlatanism
jedishrfu
jedishrfu is offline
#2
Dec3-12, 02:18 PM
P: 2,473
combination is right you're selecting letters, numbers and more letters:

Choices for each character of your 6 charcter code:

24 * 24 * 8 * 8 * 24 * 24 = total number of codes possible

Now if these could be rearranged then you'd have to worry about permutations to elimnate repeats in your counts.
reldridge
reldridge is offline
#3
Dec3-12, 02:22 PM
P: 5
Thank you -

So de-duping these down to create 2.5 million unique codes using this formula will not be an issue, sense there are 21,233,664 possibilities.

jedishrfu
jedishrfu is offline
#4
Dec3-12, 02:39 PM
P: 2,473

creating a random combination


okay what do you mean by de-duping?
reldridge
reldridge is offline
#5
Dec3-12, 02:46 PM
P: 5
Well sense this is just a random generator out of excel the possibility of it creating a duplicate is there, so i will need to just remove dupes, or nth select down to 2.5 million unique codes.

Just needed to make sure that the 6 digit using that formula could create that many unique codes.
phinds
phinds is offline
#6
Dec3-12, 02:51 PM
PF Gold
phinds's Avatar
P: 5,676
Quote Quote by reldridge View Post
Well sense this is just a random generator out of excel the possibility of it creating a duplicate is there ...
So you have a belief that "true" random would not include any dupes?

How would you create 100000 consecutive random numbers from 1 to 100 ?
jedishrfu
jedishrfu is offline
#7
Dec3-12, 03:02 PM
P: 2,473
this reminds of how new programmers used to construct a deck of randomly sorted cards.

generate a number from 0-51 check if its present in the crd deck array if so then generate another.

The better approach is to generate a sorted sequence of cards into an array and then to randomly shuffle two cards by selecting two indexes at random and swapping the cards.
reldridge
reldridge is offline
#8
Dec3-12, 03:22 PM
P: 5
Quote Quote by phinds View Post
So you have a belief that "true" random would not include any dupes?
No belief, was just stating that there could be duplicate codes during the random selection and i would need to remove the duplicates until reaching my goal of 2.5 unique codes...
reldridge
reldridge is offline
#9
Dec3-12, 03:23 PM
P: 5
Thanks for the help.


Register to reply

Related Discussions
Combinations Precalculus Mathematics Homework 8
Combinations (How many combinations contain specific numbers)? Calculus & Beyond Homework 2
Sum of combinations Precalculus Mathematics Homework 12
Combinations Precalculus Mathematics Homework 2
Combinations of a set Programming & Computer Science 3