# Unfamiliar notation that looks like a vector but isnt

This topic is 4311 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

I'm trying to get my head around a certain equation (well, actually a few), but they have this notation that I initially thought was a vector with 2 elements, but when I worked through it I found that didnt make sense... Luckily in the paper I was reading it gives the parameters and the answer, but I dont get how they have got from one to the other e.g. (assume the little brackets are big ones)
126 = (9)
(5)

126 = (9)
(4)

84 = (9)
(3)

36 = (9)
(7)


Wierd stuff. Anyone any clues here? Cheers, Dave.

##### Share on other sites
that's the "choose" function, used in many fields but originating in probability. as an example, lets say you had 9 types of topping for a hot dog, and you wanted to find out how many different combinations you could make by picking 5 of those toppings, 9 choose 5 is your answer, or 126.

Mathworld explanation

##### Share on other sites
Excellent! Cheers for that, you have no idea how stumped that had me. I know a little about combinatorics, but only ever seen nCk style before, never this damned ambiguous notation!

Thanks again,

1. 1
Rutin
25
2. 2
3. 3
JoeJ
19
4. 4
5. 5

• 10
• 11
• 9
• 9
• 10
• ### Forum Statistics

• Total Topics
631753
• Total Posts
3002098
×

## Important Information

We are the game development community.

Whether you are an indie, hobbyist, AAA developer, or just trying to learn, GameDev.net is the place for you to learn, share, and connect with the games industry. Learn more About Us or sign up!

Sign me up!