function piva=PiMonterCarlo(n)
x=0;y=0;d=0;
m=length(n);
pivalue=zeros(m,1);
for i=1:m
    x=2*rand(n(i),1)-1;
    y=2*rand(n(i),1)-1;
    d=x.^2+y.^2;
    pivalue(i)=4*sum(d<=1)/n(i);
end
if nargout==0
    if m>1
        figure;
        plot(n,pivalue,'k.');
        h=refline(0,pi);
        set(h,'linewidth',2,'color','r');
        text(1.05*n(end),pi,'\pi','FontSize',15);
        xlabel('投點(diǎn)個(gè)數(shù)');
        ylabel('\pi的模擬值');
    else
        figure;
        plot(x,y,'r.');
        hold on;
        h=rectangle('Position',[-1 -1 2 2],'LineWidth',2);
        t=linspace(0,2*pi,100);
        plot(cos(t),sin(t),'k','LineWidth',2);
        xlabel('X');ylabel('Y');
%         title('Pi的模擬值:'num2str(pivalue));
        axis([-1.1 1.1 -1.1 1.1]);axis equal;
    end
else
    piva=pivalue;
end

pi.png