FileMaker Pro Custom Functions

/** * ===================================== * RandomWeightedRank ( total ) * * PURPOSE: * Returns a random integer between 1 and total such that the probability * of each number is proportional to itself. For example, 2 is twice as * likely as 1, and 3 is 3 times as likely as 1. This may be useful for * ordinally weighted lotteries, where applicants have a number of lottery * tickets determined by some ranking. For example, you might want to * randomly award a scholarship, but you might also want individuals with * greater financial need to be more likely to receive the scholarship. * * RETURNS: * A random integer between 1 and total, inclusive. * * PARAMETERS: * total: The number of items in a list to select from. * * DEPENDENCIES: none * * HISTORY: * CREATED on 2012-02-08 by Jeremy Bante <http://scr.im/jbante>. * ===================================== */ Let ( [ ~sampleSpace = total * ( total + 1 ) / 2; // sum of all ranks ~random = Ceiling ( Random * ~sampleSpace ) // sample from "lottery" ]; // find "winning" rank as inverse of sum of ranks formula Ceiling ( ( Sqrt ( 8 * ~random + 1 ) - 1 ) / 2 ) )
 Then copy & paste into FileMaker Advanced's Edit Custom Function window.