[求助]自定义函数数据拟合问题，请求帮助

[slgu]

用模型：fx=@(b,x)b(1)*x.^b(2).*exp(-b(3)*x);
b=[8.4601097, -2.1449757, -0.40722326]
SSy = 4.7982e+005
RSS = 76312.10765
MSe = 657.86
R^2 = 0.84096

我建议您用模型：fx=@(b,x)b(1)*exp(b(2)*x+b(3)*x.^2)+b(4)*x.^b(5);
b=[0.000011922916, 28.889156, -14.105302, 7.4089767, -2.2812403]
SSy = 4.7982e+005
RSS =70060.17726
MSe = 614.56
R^2 = 0.85399
结果较好。


附小程序：
clear,clc
x=0.2:0.2:4.8;
y=[ 455.229 52.765 35.212 40.566 45.549 26.638 7.783 9.97 5.051 4.171 3.681 0.501 0 0 0 0 0 0 0 0 0 0 0 0
407.451 84.16 17.786 26.998 43.44 39.725 15.89 8.549 6.81 6.118 2.169 0.919 0.441 0 0 0 0 0 0 0 0 0 0 0
220.457 64.813 28.326 31.582 43.862 29.885 8.756 6.486 3.541 7.392 1.687 0.23 0.441 0 0 0 0 0 0 0 0 0 0 0
188.963 50.099 31.619 26.381 36.226 12.43 6.145 4.282 1.892 2.254 0 0.29 0.279 0 0.131 0 0 0 0 0 0 0 0 0
184.464 48.644 10.163 14.263 28.438 11.246 10.007 2.864 2.802 1.748 0.551 0.263 0.126 0 0.118 0 0 0 0 0 0 0 0 0];
x=[x; x; x; x; x];x1=0.15:.05:4.85;
x= x( : );
y= y( : );
plot(x,y,'o','markerfacecolor','b')
fx1=@(b,x)b(1)*x.^b(2).*exp(-b(3)*x);
b=[8.4601097, -2.1449757, -0.40722326];
y1=fx1(b,x1);
hold on
plot(x1,y1,'r-','linewidth',2)
fx2=@(b,x)b(1)*exp(b(2)*x+b(3)*x.^2)+b(4)*x.^b(5);
b=[0.000011922916, 28.889156, -14.105302, 7.4089767, -2.2812403];
y2=fx2(b,x1);
plot(x1,y2,'k-','linewidth',2)
legend('','fx1','fx2')
axis tight