（二十七）matlab 遺傳算法

初始化

function pop=initpop(popsize,chromlength)
pop=round(rand(popsize,chromlength));
end

目標函數值

function pop2=decodebinary(pop)
[px,py]=size(pop);
for i=1:py
    pop1(:,i)=2.^(py-i).*pop(:,i);
end
pop2=sum(pop1,2);
end

function pop2=decodechrom(pop,spoint,length)
pop1=pop(:,spoint:spoint+length-1);
pop2=decodebinary(pop1);
end

function [objvalue]=calobjvalue(pop)
temp1=decodechrom(pop,1,10);
x=temp1*10/1023;
% 目標函數
objvalue=10*sin(5*x)+7*cos(4*x);
end

個體適應值

function fitvalue=calfitvalue(objvalue)
global Cmin;
Cmin=0;
[px,py]=size(objvalue);
for i=1:px
    if objvalue(i)+Cmin>0
        temp=Cmin+objvalue(i);
    else
        temp=0.0;
    end
    fitvalue(i)=temp;
end
fitvalue=fitvalue';

選擇

function [newpop]=selection(pop,fitvalue)
totalfit=sum(fitvalue);
fitvalue=fitvalue/totalfit;
fitvalue=cumsum(fitvalue);
[px,py]=size(pop);
ms=sort(rand(px,1));
fitin=1;
newin=1;
while newin<=px
    if(ms(newin))<fitvalue(fitin)
        newpop(newin)=pop(fitin);
        newin=newin+1;
    else
        fitin=fitin+1;
    end
end

交叉

function [newpop]=crossover(pop,pc)
[px,py]=size(pop);
newpop=ones(size(pop));
for i=1:2:px-1
    if(rand<pc)
        cpoint=round(rand*py);
        newpop(i,:)=[pop(i,1:cpoint),pop(i+1,cpoint+1:py)];
        newpop(i+1,:)=[pop(i+1,1:cpoint),pop(i,cpoint+1:py)];
    else
        newpop(i,:)=pop(i);
        newpop(i+1,:)=pop(i+1);
    end
end

變異

function [newpop]=mutation(pop,pm)
[px,py]=size(pop);
newpop=zeros(px,py);
for i=1:px
    if(rand<pm)
        mpoint=round(rand*py);
        if mpoint<=0
            mpoint=1;
        end
        newpop(i,:)=pop(i,:);
        if any(newpop(i,mpoint))
            newpop(i,mpoint)=0;
        else
            newpop(i,mpoint)=1;
        end
    else
        newpop(i)=pop(i);
    end
end

最大適應值

function [bestindividual,bestfit]=best(pop,fitvalue)
[px,py]=size(pop);
bestindividual=pop(1,:);
bestfit=fitvalue(1);
for i=2:px
    if fitvalue(i)>bestfit
        bestindividual=pop(i,:);
        bestfit=fitvalue(i);
    end
end

主程序

popsize=20;
chromlength=10;
pc=0.7;
pm=0.005;
pop=initpop(popsize,chromlength);
for i=1:20
[objvalue]=calobjvalue(pop);
fitvalue=calfitvalue(objvalue);
[newpop]=selection(pop,fitvalue);
[newpop]=crossover(pop,pc);
[newpop]=mutation(pop,pc);
[bestindividual,bestfit]=best(pop,fitvalue);
y(i)=max(bestfit);
n(i)=i;
pop5=bestindividual;
x(i)=decodechrom(pop5,1,chromlength)*10/1023;
pop=newpop;
end
fplot(@(x)9.*sin(5.*x)+8.*cos(4.*x),[0 15])
hold on
plot(x,y,'r*')
hold off

參考資料：《MATLAB R2016a 完全自學一本通》