### plot默认是实线连接，离散的数据使用默认plot时，会连起来
x1=0:16; y1=1./((x1-2).^2+1)+1./((x1-9^.2+4))+5; x2=0:0.02:16; y2=1./((x2-2).^2+1)+1./((x2-9^.2+4))+5; subplot(2,2,1),plot(x1,y1,'rp'),axis([0 17 5 6.2]),title('Picture 1'),grid on subplot(2,2,2),plot(x2,y2,'rp'),axis([0 17 5 6.2]),title('Picture 1'),grid on subplot(2,2,3),plot(x1,y1,'rp'),axis([0 17 5 6.2]),title('Picture 1'),grid on subplot(2,2,4),plot(x2,y2,'rp','linewidth',2),axis([0 17 5 6.2]),title('Picture 1'),grid on