绘制曲线问题！

x1=[0,6,12,18,24,30]
y1=[0.642,1.276,1.516,2.123,2.427,2.623]
x2=[0,6,12,18,24,30]
y2=[1.037,1.711,2.158,2.348,2.484,2.828]
x3=[0,6,12,18,24,30]
y3=[1.185,1.798,2.084,2.274,2.417,2.535]
x4=[0,6,12,18,24,30]
y4=[1.076,1.849,2.282,2.764,2.954,2.856]
x5=[0,6,12,18,24,30]
y5=[0.989,1.694,2.063,2.279,2.293,2.571]
x6=[0,6,12,18,24,30]
y6=[0.524,0.550,0.565,0.560,0.580,0.583]
x7=[0,6,12,18,24,30]
y7=[1.028,1.905,2.332,2.679,2.867,2.741]
plot(x1,y1,x2,y2,x3,y3,x4,y4,x5,y5,x6,y6,x7,y7)
set(gca,'xtick',[0,6,12,18,24,30]);
set(gca,'ytick',[0:0.1:3.5]);
legend('1','2','3','4','5','6','7',1)
grid on
xlabel('t(h)')
ylabel('OD(500nm)')

请问怎么才能让这些曲线平滑？（不是两点一线画）

还有，画y=-0.0010x^2+0.0953x+0.6552 的命令是什么？