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 ')
VIP
