How to make nPr formula as the perms function makes nPn only ?

How to make nPr formula as the perms function makes nPn only ?

Answer 1

[Ayden Clay]

Hey Abdelrhman,

The nchoosek function ought to be what you're looking for.

It can provide the binomial coefficient for

b = nchoosek(n,k);

or every permutation for

C = nchoosek(v,k);

where v is a row or column vector (length < 15). For example, where v = [1,2,3,4]; and k = 2; we get:

C = nchoosek([1,2,3,4],2)
C =
     1     2
     1     3
     1     4
     2     3
     2     4
     3     4

and if you just want the number, you can ask for size(C,1).

sz1 = size(C,1)
sz1 =
     6
     

Or you can do it in one move with:

sz1 = size(nchoosek([1,2,3,4],2),1)
sz1 =
     6

I hope this helped!