Question

用MATLAB拟合函数，关系式y=a/(b+x^(-c))，求参数a b c的值

XY=[25,3.1;100,6.06;225,7.99;400,9.52;625,10.81;900,11.93;1225,12.93;1600,13.84;2025,14.65;2500,15.41;3025,16.14;3600,16.82;4225,17.47;4900,18.08;5625,18.65;6400,19.22;7225,19.75;8100,20.25;9025,20.73;10000,21.18];
给算一下吧！
有MATLAB的安装包么 32位的 发给我 呗~

Answer 1

XY=[25,3.1;100,6.06;225,7.99;400,9.52;625,10.81;900,11.93;1225,12.93;1600,13.84;2025,14.65;2500,15.41;3025,16.14;3600,16.82;4225,17.47;4900,18.08;5625,18.65;6400,19.22;7225,19.75;8100,20.25;9025,20.73;10000,21.18];
y=XY(:,1);
x=XY(:,2);
plot(x,y)
f=@(a,x) a(1)./(a(2)+x.^(-a(3))); %拟合形式，数组a即代表[a,b,c]
a0=[0,8,1];  % 假设初始值
r=lsqcurvefit(f,a0,x,y);
hold on
plot(x,r(1)./(r(2)+x.^(-r(3))),'r--')
legend('拟合前','拟合后')
disp(r)

我有2013a的matlab，https://yunpan.cn/cLaNjSaDh7Y4p  访问密码 c27f

Answer 2

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[x,I]=sort(x);y=y(I);%由于你的数字是杂乱的,我排列一下
f=@(a,x)a(1).*x.^(a(2))+a(3); %拟合形式，数组a即代表[a,b,c]
a0=[1,0.02,-5]; % 假设初始值
r=lsqcurvefit(f,a0,x,y);
%非线性拟合
%拟合结果保存在r=[a,b,c]
plot(x,y)
hold on
plot(x,r(1)*x.^r(2)+r(3),'r--')
legend('拟合前','拟合后')
disp(r)

追问

我要结果 a= ,b= ,c= .

Answer 3

>> XY=[25,3.1;100,6.06;225,7.99;400,9.52;625,10.81;900,11.93;1225,12.93;1600,13.84;2025,14.65;2500,15.41;3025,16.14;3600,16.82;4225,17.47;4900,18.08;5625,18.65;6400,19.22;7225,19.75;8100,20.25;9025,20.73;10000,21.18];
>> x=XY(:,1);
>> y=XY(:,1);
>> syms t;
f=fittype('a/(b+t^(-c))','independent','t','coefficients',{'a','b','c'});
cfun=fit(x,y,f)
结果：

cfun =

General model:
cfun(t) = a/(b+t^(-c))
Coefficients (with 95% confidence bounds):
a = 1 (1, 1)
b = -2.647e-014 (-9.633e-014, 4.339e-014)
c = 1 (1, 1)

这里括号里的值是置信区间

追问

a=多少 b=多少 c=多少 我要结果谢谢