clear
scalar beta0 = 1.5
scalar beta1 = 5.6
scalar sigma = 2
forvalues i = 1(1)50 {
    set obs 100
    gen x`i' =_n
    gen u`i' = invnorm(uniform())*sigma
    gen y`i'= beta0 + beta1*x`i'+u`i'      
    quietly reg y`i' x`i'
    matrix b`i' = e(b)
    matrix list b`i'
    matrix rmse`i'= e(rmse)
    matrix list rmse`i'
}
matrix b0 = (0,0)
matrix rmse0 = (0)
forvalues j = 1(1)50 {
   matrix b0 = b0\b`j'
   matrix b`j' = b0
   matrix rmse0 = rmse0\rmse`j'
   matrix rmse`j' = rmse0
   matrix list b`j'
   matrix list rmse`j'
}
matrix list b50
matrix list rmse50
matrix U = J(1,51,1)
matrix list U

以上，虽然看了输出结果和help，但是还是不怎么能理解matrix的意义。请教