_ Matlab的曲线拟合向导

发信人: lll (Paper.9.3), 信区: MathTools
标 题: Matlab的曲线拟合向导
发信站: BBS 水木清华站 (Mon Oct 20 19:41:02 2003), 转信

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近来询问曲线拟合问题的比较? 
这是lll同学给出的一个总结。 
向lll表示感谢。 
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%只考虑线性拟合

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%原始数据 
t = [0 .3 .8 1.1 1.6 2.3]';
y = [0.5 0.82 1.14 1.25 1.35 1.40]';

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%多项式拟合 


p=polyfit(t,y,2)

%利用左除
X = [ones(size(t)) t t.^2];
a = X\y

%regress函数
X = [ones(size(t)) t t.^2];
b=regress(y,X)

%lsqcurvefit函数
fun=inline('x(1)*t.^2+x(2)*t+x(3)','x','t');
x=lsqcurvefit(fun,[0,0,0],t,y)

%Curve Fitting Toolbox
fit1= fit(t,y,'poly2')

%Curve Fitting Toolbox(自定义多项式)
mymodel = fittype('a*t^2+b*t+c','independent','t');
%mymodel = fittype('a*x^2+b*x+c');
fit1= fit(t,y,mymodel,'start',[0,0,0])

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%指数形式的拟合


X = [ones(size(t)) exp(-t) t.*exp(-t)];
a = X\y


%lsqcurvefit函数
fun=inline('x(1)+x(2)*exp(-t)+x(3).*t.*exp(-t)','x','t');
x=lsqcurvefit(fun,[0,0,0],t,y)


%Curve Fitting Toolbox
mymodel = fittype('a+b*exp(-t)+c*t*exp(-t)','independent','t');
%mymodel = fittype('a+b*exp(-x)+c*x*exp(-x)');
fit1= fit(t,y,mymodel,'start',[0,0,0])

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%不含常数项的多项式拟合
%利用左除
X = [t t.^2];
a = X\y


%regress函数
X = [t t.^2];
b=regress(y,X)


%lsqcurvefit函数
fun=inline('x(1)*t.^2+x(2)*t','x','t');
x=lsqcurvefit(fun,[0,0],t,y)


%Curve Fitting Toolbox
mymodel = fittype('a*t^2+b*t','independent','t');
%mymodel = fittype('a*x^2+b*x');
fit1= fit(t,y,mymodel,'start',[0,0])

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