function[change] = delta(ct,mt,y,b)% The delta function is the non-uniform distributions used by the nonUniform% mutations.  This function returns a change based on the current gen, the% max gen and the amount of possible deviation.%% function[change] = delta(ct,mt,y,b)% ct - current generation% mt - maximum generation% y  - maximum amount of change, i.e. distance from parameter value to bounds% b  - shape parameter% Binary and Real-Valued Simulation Evolution for Matlab % Copyright (C) 1996 C.R. Houck, J.A. Joines, M.G. Kay %% C.R. Houck, J.Joines, and M.Kay. A genetic algorithm for function% optimization: A Matlab implementation. ACM Transactions on Mathmatical% Software, Submitted 1996.%% This program is free software; you can redistribute it and/or modify% it under the terms of the GNU General Public License as published by% the Free Software Foundation; either version 1, or (at your option)% any later version.%% This program is distributed in the hope that it will be useful,% but WITHOUT ANY WARRANTY; without even the implied warranty of% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the% GNU General Public License for more details. A copy of the GNU % General Public License can be obtained from the % Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.r=ct/mt;if(r>1)  r=.99;  % disp(sprintf('max gen %d < current gen %d setting ratio = 1',mt,ct));endchange = y*(rand*(1-r))^b;