I have no idea why they might be missing sometimes, but not always. What I
would say is that this is not the most convenient method to store these
results. For one, -simulate- can do much of the work involved in storing. If
you insist on more control over this process, try the -postfile- suit of
commands (http://www.stata-journal.com/article.html?article=pr0036)
HTH
Martin
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Patrick P.
Phillips
Sent: Tuesday, October 14, 2008 11:09 AM
To: [email protected]
Subject: st: RE: RE: Curious missing scalar after regress postestimation
Thanks, Martin, for your reply. It usually works fine for me (it does so in
around 1800 of the 2000 simulations) which is why it is so infuriating.
The difficulty is that the scalar appears non-missing when I type 'scalar
list all', but when I try to use (in a calculation, post results or just
display) it appears to be missing!
Any other thoughts?
Many thanks in advance,
Patrick
PS Martin, originally it was scalar var_alpha = _se[alpha]^2, but I
simplified it for the post. You are correct that that could lead to problems
later on!
______________________________
Patrick Phillips
Statistician
MRC Clinical Trials Unit
222 Euston Road
London NW1 2DA
________________________________________
From: [email protected]
[[email protected]] On Behalf Of Martin Weiss
[[email protected]]
Sent: 14 October 2008 09:59
To: [email protected]
Subject: st: RE: Curious missing scalar after regress postestimation
Works for me when I try it with another example.
*********
sysuse census, clear
tabulate region, gen(region)
regress death medage region2-region4 [aw=pop], noc vce(cluster state)
scalar var_medage = _se[medage]
di var_medage
scalar est_medage = _coef[medage]
di est_medage
*********
Sure you do not do anything in between storing and -display-ing that erases
your -scalar-s? Why not use packages like -ssc d parmest- or Stata`s -
estimates store- for this purpose?
BTW, probably dangerous to call the standard error of the OLS estimator
"var_...". Could lead to misinterpretations down the road...
HTH
Martin
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Patrick P.
Phillips
Sent: Tuesday, October 14, 2008 10:44 AM
To: [email protected]
Subject: st: Curious missing scalar after regress postestimation
I am running some simulations including a regress command and have come
across some curiosities with scalars.
I run the following commands:
regress beta alpha [aweight=prec], nocons vce(cluster trial)
scalar var_alpha = _se[alpha]
scalar est_alpha = _coef[alpha]
scalar r_sqrd = e(r2)
When I type scalar list, I get the following:
. scalar list
r_sqrd = .09759686
est_alpha = .42516408
var_alpha = .48875057
But, when I try to display the contents of scalar var_alpha, it appears to
only contain '.':
. disp var_alpha
.
Any thoughts on why this is? It's driving me mad!
Many thanks for your help,
Patrick
______________________________
Patrick Phillips
Statistician
MRC Clinical Trials Unit
222 Euston Road
London NW1 2DA
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