function par = parents(pop,method,varargin)% PARENTS - Selects parents from a given population.%% par=parents(population,'method',option1,option2,etc..)% There are several different methods that parents can be selected% from a population. Given the population, method and options the% function will return an even number of parents in an Nx2 matrix.% If the population is an odd number X then N=(X-1)/2%% [parent1_XX parent1_XY%  parent2_XX parent2_XY%     .          . %     .          .%  parentN_XX parentN_XY];% % The following methods and options are supported%% 'rand'   - random selection%   options:%   'elim'  - prevent a member from being selected twice (default)%   'keep'  - keep the member in the parent pool%% 'lin'    - linear fitness %   options:%   'elim'  - prevent a member from being selected twice (default)%   'keep'  - keep the member in the parent pool%% 'quad'   - quadratic fitness%   options:%   'elim'  - prevent a member from being selected twice (default)%   'keep'  - keep the member in the parent pool%% 'best'   - best members allways selected NOT IMPLEMENTED YET%   options:%   top    - use this number of best members (default 4)%   'rand' - select from remaining parent pool using 'rand' (default)%   'lin'  - select from remaining parent pool using 'lin'%   'quad' - select from remaining parent pool using 'quad'%% The number of desired parents can also be% selected this argument when specified should be the last in the% function call, if omitted the entire population will be paired.%% Examples:%% par=parents(pop,'quad') pair up the population with quadratic fitness.%% par=parents(pop,'lin',6) create 6 parents i.e. 3 pairs using% linear fitness and preventing a member from being selected twice.%% par=parents(pop,'best',4,'rand,'keep') will give parents where% the top 4 best members are randomly matched with the rest of the% members in the poplation.  %% par=parents(pop,'best','rand',6) same as above, 3 pairs will be% selected from the top 4 best members, in this case however the top 3% best member will be randomly paired with a member from the rest of% the parent pool, again preventing any member from being selected% twice.%% See also CHILDREN,MUTATE%------------------------------------------------------------pop=tagem(pop);%------------------------------------------------------------if strcmp(method,'best')  nmbr_par=0;  bmethod=find_boption(pop,varargin);  for k=1:length(varargin)    if isa(varargin{k},'double')      nmbr_par=varargin{k};      repeat=length(pop)/(2*nmbr_par);      break    end  end  if ~nmbr_par    nmbr_par=1;				% this should be default    repeat=length(pop)/2;                % not good though  endelse  nmbr_par=number_of_par(pop,varargin);  repeat=length(pop)/nmbr_par;endopt=find_option(pop,varargin);cp=[];if mod(length(pop),nmbr_par)  error('Bad number of parents')endfor l=1:repeat    switch method				   case 'rand'				    par=pair_pop(pop,method,opt,nmbr_par);   case 'lin'    par=pair_pop(pop,method,opt,nmbr_par);   case 'quad'    par=pair_pop(pop,method,opt,nmbr_par);      case 'best'        pop=fliplr(sort(pop));    bpar=pop(1:nmbr_par);        for k=1:nmbr_par      pop=del_chrom(pop,bpar(k));    end        for k=1:nmbr_par;      w=make_wheel(pop,bmethod);      tmp(k)=spin_wheel(pop,w);      if strcmp(opt,'elim')	pop=del_chrom(pop,tmp(k));      elseif strcmp(opt,'keep')	pop=pop;      else	error('wrong option')      end    end    par(:,1)=bpar;    par(:,2)=tmp;      otherwise    error('wrong method')  end  cp=[cp      par];endpar=cp;%==============END MAIN=============================================function par = pair_pop(pop,method,opt,nmbr_par)% PAIR_POP - %   for k=1:nmbr_par;  w=make_wheel(pop,method);  tmp(k)=spin_wheel(pop,w);  if strcmp(opt,'elim')    pop=del_chrom(pop,tmp(k));  elseif strcmp(opt,'keep')    pop=pop;  else    error('wrong option')  endendpar(1:nmbr_par/2,1)=tmp(1:2:end-1); par(1:nmbr_par/2,2)=tmp(2:2:end);%=============END PAIR_POP===============================================function w = make_wheel(c,method)% MAKE_WHEEL - This function makes the roulette wheel. %   switch method case 'rand'  n=length(c);  w=linspace(0,1,n+1);  w=w(2:end); case 'lin'  pol=rand(1,2);  for k=1:length(c)    fit(k)=polyval(pol,get(c(k),'fitness'));  end  for k=1:length(c)    w(k)=sum(fit(1:k))/sum(fit);  end case  'quad'  pol=rand(1,3);  for k=1:length(c)    fit(k)=polyval(pol,get(c(k),'fitness'));  end  for k=1:length(c)    w(k)=sum(fit(1:k))/sum(fit);  endend%================END MAKE_WHEEL==============================function winner = spin_wheel(pop,w)% SPIN_WHEEL - This function spins the roulette wheel and returns% the winner.win=rand;for k=1:length(w)  if win<=w(k)    winner=pop(k);    break  endend%===============END SPIN_WHEEL===============================function pop = del_chrom(pop,dchrom)% DEL_CHROM - Deletes a chromosome from a vector of% chromosomes.id=get(dchrom,'id');ind=find_id(pop,id);if ~ind  pop=pop;  returnendn=length(pop);if and(ind==1,n==1)  pop=chrom;elseif ind==1  pop=pop(2:end);  return;elseif ind==n;  pop=pop(1:end-1);  return;else  pop=[pop(1:ind-1) pop(ind+1:end)];end%===============END DEL_CHROM================================function ind=find_id(chr,id)ind=0;for k=1:length(chr)  if strcmp(get(chr(k),'id'),deblank(id));    ind=k;    break  endend  function nmbr=number_of_par(pop,options);n=length(pop);if mod(n,2)  error('There must be an even number of members in the population')endif ~length(options)  nmbr=n/2;  breakelse  for k=1:length(options)    if isa(options{k},'double')      tst_nmbr=options{k};      if tst_nmbr>n | mod(tst_nmbr,2)	error('Wrong number of parents, read the help')      else	nmbr=tst_nmbr;	break      end    else      nmbr=n/2;    end  endend   function opt=find_option(pop,options)if isempty(options)  opt='elim';  break;endfor k=1:length(options)  if isa(options{k},'char')    if strcmp(options{k},'elim')|strcmp(options{k},'keep')      opt=options{k};      break    else      opt='elim';    end  else    opt='elim';  endendfunction opt=find_boption(pop,options)if isempty(options)  opt='rand';  break;endopt='';for k=1:length(options)  if isa(options{k},'char')    if ~strcmp(options{k},'elim')|strcmp(options{k},'keep')      switch options{k}       case 'lin'	opt='lin';	break       case 'quad'	opt='quad';	break;       case 'rand'	opt='rand';	break;       otherwise	error('wrong option')      end    end  endendif isempty(opt)  opt='rand';end