fnRandom ( minValue ; maxValue )

A better random, between a min and max value

Average rating: 4.7 (24 votes) Log in to vote

Rob Poelking - Show more from this author
Kiza Solutions
https://kizasolutions.com

Sample input:

fnRandom ( -20; 30; 1 )

Sample output:

-2.2

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

/*
 * ==================================================================
 * fnRandom ( minValue ; maxValue ; PrecisionDigits)
 *
 * PARAMETERS:
 *            @minValue (num) minimum number value
 *            @maxValue (num) maximum number value
 * RETURNS:
 *            (number) random value between min and 
 *            max inclusively
 * DEPENDENCIES:
 *            none
 * PURPOSE:
 *            Produce any number between minimum
 *            and maximum. 
 * NOTES:
 *            none
 * AUTHOR:
 *            Rob Poelking
 * REVISIONS:
 *            2013-12-30 Rob Poelking - initial release
 *            2014-01-02 Rob Poelking - simplified based 
 *            on user feedback.
 *            2016-12-02 Rob Poelking - restored original version
 *            with added precision after discovering an error when
 *            min and max were both 1 and precision of 0. Result was
 *            occassionally 2
 * ==================================================================
 *
 */

Let ([
	mn = minValue;
	mx = maxValue ;
	prec = PrecisionDigits ; 
	delta = mx - mn + 1;
	ex = Ceiling ( Log ( delta ) )  ;
	v = Random;
	offset = Mod ( Round( v * 10^ex ; prec )   ; delta )
	];
	mn + offset
)

I have always found FileMaker's built in Random function completely useless on it's own. Not that the function IS useless, but the random value I always needed was some whole integer. So I was always multiplying it and rounding it. Other times, I needed values that were between a minimum and a maximum. This function solved that particular issue for me.

The problem with the suggested calculation minValue + Round ( Random * ( maxValue - minValue + 1 ); PrecisionDigits ) was that if min and max are 1 and precision is 0, then you could get 2 erroneously.

Comments

		comment, VR Jan 1, 2014
Couldn't it be simpler? minValue + Int ( Random * ( maxValue - minValue + 1 ) )

		Rob, Monk Media Dec 2, 2016
VR - just discovered an error that when min and max are both 1 and precision is 0, then you could get 2 as a result which would be wrong. I know you're thinking, why would you ever do that but programmatically fetching a random value that could cycle down (as in a loop) you could get the wrong value.

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

fnRandom ( minValue ; maxValue )

Comments

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