ployfit2.m

多项式二次曲线拟合程序！用于实验设计！另有画图函数并且可以进行方差分析1

function  [A,B,C]=ployfit2(x,y)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%ployfit2 -> a basic function used for 2 polynomial fit!
%
%USAGE : [A,B,C]=ployfit2
%
%Arguments : save the data ! the varible is x and y.
%
%Return Values : [A,B,C] is coefficient!
%                
%
%  History        :   Author      :   caodongsheng
%                     Created on  :   2007.6.14  
%                     Comments    :   The basic ployfit algorithm.
%  
%                     ENJOY IT!
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% load x.mat
% load y.mat

data_X=x;
data_Y=y;
[m,n]=size(data_X);
if m~=size(data_Y,1)
    disp('you have a wrong data used to input!')
    diap('Plwase reapt to input the data!')
end

% data_X=data_X-ones(m,1)*mean(data_X);
% % s=ones(m,1)*std(data_X);
% % data_X=data_X./sqrt(s);
% %  
% data_Y=data_Y-ones(m,1)*mean(data_Y);
k=1;
for i=1:n
    for j=i:n
        A1_part(:,k)=data_X(:,i).*data_X(:,j);
        k=k+1;
    end
end
% A1_part
A2_part=data_X;
A3_part=ones(m,1);
AA=[A1_part,A2_part,A3_part];
BB=data_Y;
c=pinv(AA)*BB;
% c=pinv(AA'*AA)*AA'*BB;

clear i j
% C=zeros(n);
C=[];

for i=1:n
    row=size(c);
    cds=c(1:n-i+1,1);
    cds=cds';
    if size(cds,2)~=n
       cds=[zeros(1,n-size(cds,2)),cds];
    end
    C=[C;cds];
    c=c((n-i+2):row,:);
end
cc=(C-tril(C))/2;
ccc=cc';
C=cc+tril(C)+ccc;
B=c(1:n,:);
A=c(n+1);