命令：
program MyOLS3
args lfn beta sigma
quietly {
replace ‘lfn’ = ln(normalden($ML_y1, ‘beta’, ‘sigma’))
}
end
ml model lf MyOLS3 (y = eduyear1 experi experi2nonruralspeci marriage health middle west) /sigma, tech(nr 5bfgs 5 dfp 5bhhh 5)
ml check
mlsearch
ml max
从mlcheck 开始，出现问题：

Test 1:Calling MyOLS3 to check if it computes log likelihood and
does not alter coefficient vector...
opt__eval_cycle():3301subscript invalid
opt__eval(): -function returned error
_optimize_evaluate(): -function returned error
_mopt__evaluate(): -function returned error
mopt__check_test1(): -function returned error
_moptimize_check(): -function returned error
Mopt_check(): -function returned error
<istmt>: -function returned error
r(3301);