RandNormal ( mean ; stdDev )

Generates a random number drawn from a normal (Gaussian) distribution with a given mean and standard deviation.

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Michael Horak - Show more from this author
*COMMENT Visual Realisation

Sample input:

RandNormal ( 0 ; 1 )

RandNormal ( 0 ; 1 )

RandNormal ( 0 ; 1 )

Sample output:

-3.34772392391134908307

.0001790309728755547

3.326775098525

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

/*
RandNormal function

Author
*COMMENT Visual Realisation

Format
RandNormal ( mean ; stdDev ) 

Parameters
mean - any numeric expression or field containing a numeric expression
stdDev - any numeric expression or field containing a numeric expression

Data type returned
number

Description
Returns a random number drawn from a normal (Gaussian) distribution with a given mean and standard deviation.

May 25, 2007
*/


Let ( [
x = 2 * Random - 1 ; 
y = 2 * Random - 1 ; 
s = x^2 + y^2 
] ;
Case ( 
s > 1 ; RandNormal ( mean ; stdDev ) ; 

Let ( [
w = Sqrt ( ( -2 * Ln ( s ) ) / s ) ; 
z = x * w 
] ;
z * stdDev + mean
)

)
)

Generates a random number drawn from a normal (Gaussian) distribution with a given mean and standard deviation, using the Box-Muller algorithm. A new random number is generated every time the formula is evaluated.

To draw a number from the "standard" normal distribution, use the values of 0 for mean and 1 for stdDev.

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Note: these functions are not guaranteed or supported by BrianDunning.com. Please contact the individual developer with any questions or problems.

RandNormal ( mean ; stdDev )

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