matlab多项式曲线拟合polyfit，x,y,n

x=[ -3 -1 0 2 5.5 7];

y=[3.3 4.5 2.0 1.5 2.5 -1.2];

p3=polyfit(x,y,3);

p4=polyfit(x,y,4);%次数

p5=polyfit(x,y,5);

xcurve=-3.5:0.1:7.2;%生成x的值

p3curve=polyval(p3,xcurve);

p4curve=polyval(p4,xcurve);%计算在这些x点的多项式

p5curve=polyval(p5,xcurve);

plot(xcurve,p3curve,\'--\',xcurve,p4curve,\'-.\',xcurve,p5curve,\'-\',x,y,\'*\');

lx=[-1 1.5];

ly=[0 0];

hold on

plot(lx,ly,\'--\',lx,ly-1.3,\'-.\',lx,ly-2.6,\'-\');

text(2, 0,\'degree3\');

text(2, -1.3,\'degree4\');

text(2, -2.6,\'degree5\');