% 输入数据
x=[-0.0003 -0.0212 -0.035 -0.0474 -0.0637 -0.0755 -0.0755 -0.0814 -0.0892 -0.0964 -0.0997 -0.1121 -0.1199 -0.1467 -0.1565 -0.1611 -0.1663 -0.1729 -0.1788 -0.1833 -0.1873 -0.1931 -0.1977 -0.2023 -0.2069 -0.2134 -0.2225 -0.2317 -0.2382 -0.2454 -0.2526 -0.2578 -0.2624 -0.2676 -0.2748 -0.2846 -0.2944 -0.3016 -0.3108 -0.3219 -0.333 -0.3435 -0.3539 -0.3657 -0.3735 -0.3879 -0.3997 -0.4101 -0.4193 -0.4395 -0.452 -0.4592 -0.469 -0.4788 -0.4912 -0.4997 -0.5095 -0.5199 -0.5324 -0.5408 -0.552 -0.5598 -0.5709 -0.5794 -0.5892 -0.601 -0.6121 -0.6193 -0.6284 -0.635 -0.6428 -0.6546 -0.6644 -0.6716 -0.6781 -0.6729]';
y=[0.0007 -0.0022 -0.0036 -0.0065 -0.0109 -0.0138 -0.0138 -0.0167 -0.0196 -0.0225 -0.0255 -0.0313 -0.0356 -0.0531 -0.0589 -0.0633 -0.0662 -0.0705 -0.0735 -0.0778 -0.0807 -0.0851 -0.088 -0.0924 -0.0967 -0.1025 -0.1127 -0.1215 -0.1273 -0.136 -0.1418 -0.1476 -0.1535 -0.1593 -0.168 -0.1767 -0.1898 -0.1985 -0.2131 -0.2262 -0.2407 -0.2538 -0.2684 -0.2829 -0.2931 -0.3149 -0.3324 -0.3455 -0.36 -0.3891 -0.4065 -0.4211 -0.4371 -0.4502 -0.4705 -0.4836 -0.4996 -0.5171 -0.5389 -0.552 -0.5695 -0.584 -0.6015 -0.6189 -0.6364 -0.6567 -0.6756 -0.6902 -0.7033 -0.7193 -0.7324 -0.7542 -0.7716 -0.7862 -0.7964 -0.7876]';
fx=@(b,x)(b(1)*x+b(2)*x.^3)./(1+b(3)*x+b(4)*x.^2); % 输入模型
b=[0.14 48 -13.58 18.89]; %参数初值
for l=1:3 % 可随b 的变化调节循环次数
b=lsqcurvefit(fx,b,x,y)
b=nlinfit(x,y,fx,b)
end
figure(1),clf
plot(x,y,'o','markersize',10,'markerfacecolor','b')
hold on
x1=min(x):range(x)/230:max(x);
y1=fx(b,x1);
plot(x1,y1,'r-','linewidth',3)
legend('data','fit','location','best')
nh82.jpg
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2011-9-8 15:52 上传
