function [beta0,beta1,sigma2,R2]=linearfit0(x,Y)
%LINEARFIT0 一元線性回歸
%調用格式：[beta0,beta1,meanx,meanY,lxx,lxy,lyy,sigma2,R2]=linearfit0(x,Y)
%P217例題數據：x=[38 43 49 54 60 66 71 77 82 88];Y=[20.4 20.9 22.5 23.0 24.2
%24.3 26.2 26.6 28.0 28.9];

%By：Ji Lin
%Email: linji@live.com
%Blog: http://linji526.spaces.live.com
%Date: 2007，2008/08/18

meanx=mean(x);
meanY=mean(Y);
lxx=sum((x-meanx).^2);
lyy=sum((Y-meanY).^2);
lxy=sum((x-meanx).*(Y-meanY));
beta1=lxy/lxx;
beta0=meanY-beta1*meanx;
sigma2=(lyy-beta1*lxy)/(length(x)-2);
%R2是判定系數，越接近于1，回歸效果越顯著
R2=lxy^2/(lxx*lyy);