KNOWLEDGE BASE

POWER() Function Returns NULL When Taking Odd Roots of Negative Numbers


Published: 26 Oct 2016
Last Modified Date: 27 Oct 2016

Issue

When taking the n-th (i.e. first, ninth, seventh, third) root of a negative integer numbers using the POWER() function, Tableau Desktop returns NULL.

Environment

Tableau Desktop

Resolution

Create a calculated field for odd values.
  1. Select Analysis > Create Calculated Field 
  2. In the Create Calculated Field dialog box, do the following and click OK:
  3. Name the field. In the example, this field is called "Odd values" and enter the following formula: 
    IF [Val] >= 0
    THEN POWER([Val],1/n)
    ELSE -POWER(abs([Val]), 1/n)
    END
    
  4. Define the n by the root of negative number. For example:
    IF [Val] >= 0
    THEN POWER([Val],1/3)
    ELSE -POWER(abs([Val]), 1/3)
    END

Additional Information

For the even values of n, the result of the following calculated field is correct POWER([Value],1/n), for example: POWER(-2,1/2) = NULL.
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