Dana, Sigmma,
Excel does indeed give PERMUT(10,4) = FACT(10) / FACT(6).
In the first posts I did not recognize this.
Permutations (of a group of k *different* elements) are however (AFAIK) the
number of ways these elements can be arranged without any element being
repeated in any of these sorts.
Example : a, b, c thus k = 3
abc, acb, bac, bca, cab, cba are the six different sorts and thus P(3) = 6
{ P3 = 6! = Fact(6) }
Variations ( from a group of k elements out of a group of n *different*
elements) are (again AFAIK) the number of ways groups of k elements can be
taken out of the group of n elements and be permutated.
Example : n elements (a, b, c, d) are grouped and permutated in groups of 2
..
ab, ac, ad, ba, bc, bd, ca, cb, cd, da, db, dc are the twelve different
(permutated) groups :
2
V = n! / (n-k)! = 4! / 2! = 12 (It is this what Excel call
Permutations : Permut(n,k) )
4
Finally : Combinations are the number of Variations, whereby however the
various groups aren't permutated.
So : ab and ba aren't different. Both form the same combination.
Example : Same n elements (a,b,c,d) in groups of 2.
ab, ac, ad, ba, bc, bd, cd, are the six possible combinations :
2
C = n! / ( k! * (n-k)! ) = 4! / (2! * 2!) = 6 ( Excel : Combin(n,k)
4
So the first misunderstanding between Sigmma and me arose when I didn't
recognize the way Excel called Permutations what I know as Variations.
I therefore gave Sigmma the (in my opinion correct) formula of Permutations
and in defining them arose the second misunderstanding about the repetition
of the figures ( elements) which isn't allowed in both Permutations and
Variations.
( Better : They are allowed, but then the names and the formula's should be
different)
Conclusive :
1) I should have been aware of the way Excel calls Permutations what I know
to be Variations
( Not sure but this is maybe a difference in English and Dutch
nomenclature ?? )
2) Sigmma anyhow now has the routine ( which I have named Sub Variations )
that creates the Variations / Permutations.
--
Regards,
Auk Ales
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