怎样看 weighted least square(加权最小二乘法) code

土豆泥

这是关于加权最小二乘法的code:

proc reg data=market;

model y2=x1 x2 x3 x4;

output out=a2 p=py student=dy;

run;

data b2; set a2;

w= 1/y2;

proc reg data = b2; weight w;

model y2= x1 x2 x3 x4/r;

output out=c2 p=wpy student=wdy;

run;

这里的w=1/y2表示的是什莫呢?能不能解释一下.谢谢