checksub.m

多元线性回归：MATLAB源程序多元线性回归

%#									
%#  function [pop,rep]=checksub(newson,evson,pop,rep,chrom);		
%#									
%#  AIM:	Checks whether children strings can enter the		
%#		population, and replace a string yielding a worse	
%#		response.						
%#									
%#  PRINCIPLE:	A child string can enter the population provided that	
%#		none of its subsets already present in the population	
%#		yields a better response (otherwise, the additional	
%#		variables in the children string carry no relevant 	
%#		information for the model).				
%#		A child string entering the population replaces the 	
%#		worse non protected string.				
%#		Once a child is in the population, it must be checked 	
%#		that it is not a subset of strings already in the 	
%#		population, and yielding worse responses (as the 	
%#		additional variables contained in this string bring no 	
%#		relevant information to the model). Such worse subsets 	
%#		are replaced by null vectors (in order to keep the 	
%#		population size constant).				
%#									
%#  INPUT:								
%#	newson	: new child string to check				
%#	evson	: its associated response				
%#	pop	: the actual population, in which 'newson' might enter	
%#	rep	: the responses of the strings in the population	
%#	chrom:	: the population size					
%#									
%#  OUTPUT:								
%#	pop	: the population, after some new children strings	
%#		  have entered it, and replaced worse strings.		
%#	rep	: the response of the strings in the new population.	
%#									
%#  AUTHOR:     Delphine Jouan-Rimbaud					
%#              Copyright(c) 1997 for ChemoAC				
%#              FABI, Vrije Universiteit Brussel			
%#              Laarbeeklaan 103 1090 Jette				
%#									
%# VERSION: 1.1 (28/02/1998)						
%#								
%#  TEST:	Frederic Despagne					
%#									

function [pop,rep]=checksub(newson,evson,pop,rep,chrom);

[row,col]=size(pop);

[rep,index]=sort(rep);	% the responses are arranged in increasing order.
pop=pop(index,:);	% the strings are sorted in increasing value of response
clear index
rep=flipud(rep);	% the strings are arranged in decreasing order of response.
pop=flipud(pop);	% the strings are sorted in decreasing value of response.

n=max(find(rep>=evson));% strings from the population with a better response than the child string.
if n==[], n=0; end;

if n~=row 		% The position of newson in the sorted population would be n+1
   b=0;
   for k=1:n
	dc=newson-pop(k,:);
	if find(dc<0)==[],b=1;end;
   end
  % If b==1, at least one chrom. between 1 and n is a subset of newson, so newson is killed

   if b==1,newson=[];evson=[];end;
   clear dc

   if b==0,	% newson can enter the population. One must check that it is not subset of chrom. between
		% n+1 and chrom 
	e=[];
	for k=n+1:chrom
	   dc=pop(k,:)-newson;
	   if find(dc<0)==[],e=[e;k];end
	end
% k is the index of string of which newson is the subset.
% This string being worse than newson, it is killed, and replaced by the null vector.
clear dc

	if length(e)>=1, 
	   pop(e,:)=[];rep(e)=[];
	   pop=[pop;newson;zeros(length(e)-1,col)];
	   rep=[rep;evson;zeros(length(e)-1,1)];
	end %if length(e)>=1

	protect=[];

	if length(e)==0,

% newson is not subset of any string with a worse response.
% It enters in the population, and replaces the worse non-protected string.
% A string including n variables is protected when it gives the best response
% among all the strings including AT MOST n variables.

	   pop=[pop(1:n,:);newson;pop(n+1:chrom,:)];
	   rep=[rep(1:n);evson;rep(n+1:chrom)];

	   protect(1,1)=1;	% the best string is protected.
	   nb_var=sum(pop(1,:)); 

	   for j=2:chrom+1
		if rep(j)<rep(j-1) 
		   if sum(pop(j,:))<nb_var & sum(pop(j,:))>=1
			protect(j,1)=1;		% string j is protected
			nb_var=sum(pop(j,:));
		   else
			protect(j,1)=0;		% string j is NOT protected
		   end
		end

		if rep(j)==rep(j-1) 
		   if sum(pop(j,:))<nb_var & sum(pop(j,:))>=1
			protect(j,1)=1;		% string j is protected
			protect(j-1,1)=0;	% string j-1 is NOT protected
			nb_var=sum(pop(j,:));
		   else
			protect(j,1)=0;		% string j is NOT protected
		   end
		end
	   end % for j=2:chrom+1

	   f=find(protect==0);			% non-protected strings
	   if f~=[]
		lf=length(f);
		pop(f(lf),:)=[];		% the worse non-protected string is eliminated
		rep(f(lf),:)=[];
	   else %if f==[],			% if no strings are protected
		pop(chrom+1,:)=[];		% the worse string is eliminated
		rep(chrom+1)=[];
	   end
	end %if length(e)==0
   end %if b==0
end % if n~=row