clear

clc

xdata=[0.1732;0.1775;0.1819;0.1862;0.1905;0.1949;0.1992;0.2035;0.2079;0.2122;0.2165;0.2208;0.2252;0.2295;0.2338;0.2384];

ydata=[-3.41709;-4.90887;-6.09424;-6.95362;-7.63729;-8.12466;-8.37153;-8.55049;-8.61958;-8.65326;-8.60021;-8.52824;-8.43502;-8.32234;-8.20419;-8.04472];

%% 指定非线性函数拟合曲线

X0=[1 1];

[parameter,resnorm]=lsqcurvefit(@fun,X0,xdata,ydata); %指定拟合曲线

A=parameter(1);

B=parameter(2);

fprintf('拟合曲线Lennard-Jones势函数的参数A为：%.8f，B为：%.8f', A, B);

fit_y=fun(parameter,xdata);

figure(1)

plot(xdata,ydata,'r.')

hold on

plot(xdata,fit_y,'b-')

xlabel('r/nm');

ylabel('Fe-C Ec/eV');

xlim([0.17 0.24]);

legend('观测数据点','拟合曲线')

% legend('boxoff')

saveas(gcf,sprintf('Lennard-Jones.jpg'),'bmp');

% print(gcf,'-dpng','Lennard-Jones.png');

%% 用傅里叶函数拟合曲线

figure(2)

[fit_fourier,gof]=fit(xdata,ydata,'Fourier2')

plot(fit_fourier,xdata,ydata)

xlabel('r/nm');

ylabel('Fe-C Ec/eV');

xlim([0.17 0.24]);

saveas(gcf,sprintf('demo_Fourier.jpg'),'bmp');

% print(gcf,'-dpng','demo_Fourier.png');

function f=fun(X,r)

f=X(1)./(r.^12)-X(2)./(r.^6);

拟合曲线Lennard-Jones势函数的参数A为：0.00000003，B为：0.00103726

fit_fourier = 

     General model Fourier2:

     fit_fourier(x) =  a0 + a1*cos(x*w) + b1*sin(x*w) +

               a2*cos(2*x*w) + b2*sin(2*x*w)

     Coefficients (with 95% confidence bounds):

       a0 =       79.74  (-155, 314.5)

       a1 =       112.9  (-262.1, 487.9)

       b1 =       28.32  (-187.9, 244.6)

       a2 =        24.5  (-114.9, 163.9)

       b2 =       13.99  (-75.89, 103.9)

       w =       15.05  (3.19, 26.9)

gof = 

  包含以下字段的 struct:

           sse: 0.0024

       rsquare: 0.9999

           dfe: 10

    adjrsquare: 0.9999

          rmse: 0.0154