nchoosek Binomial coefficient or all combinations.
nchoosek(N,K) where N and K are non-negative integers returns N!/K!(N-K)!.
This is the number of combinations of N things taken K at a time.
When a coefficient is large, a warning will be produced indicating
possible inexact results. In such cases, the result is only accurate
to 15 digits for double-precision inputs, or 8 digits for single-precision
inputs.

nchoosek(V,K) where V is a vector of length N, produces a matrix
with N!/K!(N-K)! rows and K columns. Each row of the result has K of
the elements in the vector V. This syntax is only practical for
situations where N is less than about 15.

Class support for inputs N,K:
float: double, single
integer: uint8, int8, uint16, int16, uint32, int32, uint64, int64

Class support for inputs V:
float: double, single
integer: uint8, int8, uint16, int16, uint32, int32, uint64, int64
logical, char

搬自help文件

这个函数可以有很多用法，最做的东西涉及到把列数里面某个差值内的一段数选出来，就可以用nchoosek这个函数，函数名称也很有意思，n个数里面choose k个数 嘿嘿~