! y Factorial
The factorial of y
. more generally, computes the gamma function of 1+y.
! 3 6 ! i.6 1 1 2 6 24 120
x ! y Out Of
Returns y-Combinations-x. ,,y,,C,,x,, (read: x out of y or: y pick x).
. the number of ways of picking x balls (unordered) from a bag of y balls.
10!10 NB. There is only 1 way of picking all 10 balls 1 1!10 NB. There are 10 ways of choosing 1 ball from 10 10 2!10 NB. 45 ways to pick 2 out of 10 45 5!10 252
In Probability theory, also Functional Analysis (Infinite Series).
Stope Function (^!._1 y) to count permutations.
http://www.johndcook.com/blog/binomial_coefficients/ which discusses the domain of this operation. There, x!y would be represented using a pixelated image, with x on the bottom and y on the top - both surrounded by extra large parenthesis. Something like this:
y ( ) x