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XLeratorDB/statistics Documentation

SQL Server LPERMUT function


LPERMUT
Updated: 30 May 2017

Use the SQL Server scalar function LPERMUT to calculate the natural logarithm of the PERMUT function. The PERMUT function calculates the number of permutations without replacement defined as:

Syntax
SELECT [wct].[LPERMUT] (
   <@n, int,>
  ,<@k, int,>)
Arguments
Input NameDefinition
@nNumber of items
@kNumber chosen
Return Type
float
Remarks
  • If @n < 0 then NULL is returned.
  • If @k < 0 then NULL is returned.
  • If @k > n then NULL is returned.
  • Available in XLeratorDB / statistics 2008 only
Examples
Example #1
SELECT wct.LPERMUT(10,3) as LPERMUT

This produces the following result.

Example #2

Calculate the probability of 2 people having the same birthday in a room containing n people.

SELECT
     x.n
    ,1 - EXP(wct.LPERMUT(365,x.n)-wct.LPERMUTA(365,x.n)) as [p(n)]
FROM (VALUES
    (10),(20),(22),(23),(30),(57))x(n)

This produces the following result.

See Also


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