matlab拟合实例

散点图

>> x=0:0.1:1;

>> y=[0.99567,0.99334,1.0413,1.0929,1.1485,1.2619,1.3719,1.4896,1.6433,1.8117,.9981]; >> plot(x,y,'ok'),title('散点图')

多项式拟合

>> x=0:0.1:1;

>> y=log(1+x);

>> P=polyfit(x,y,3) 对观测数据x,y作3阶多项式拟合

P =

0.1079 -0.3974 0.9825 0.0004

>> xi=0:0.1:1;

>> yi=polyval(P,xi);

>> plot(x,y,'or');

>> hold on;

>> plot(xi,yi,'b');

>> plot(xi,log(1+xi),'g');

>> plot(xi,log(1+xi),'y');

>> plot(xi,log(1+xi),'g');

>> xlabel('x');

>> ylabel('y');

>> legend('采样数据','拟合曲线','精确曲线')

指数函数拟合

>> x=0:0.01:0.99;

>> y=1-sqrt(x);

>> P=polyfit(x,log(y),1)

P =

-3.3761 0.2071

>> yi=exp(polyval(P,x));

>> plot(x,y,'.k')

>> plot(x,y,'.k')

>> hold on

>> plot(x,yi,'g')

>> xlabel('x')

>> ylabel('y')

>> legend('采样数据','拟合曲线'); >> hold off;

拟合误差

>> e=yi-y;

>> plot(x,e) >> xlabel('x') >> ylabel('误差')