Re: AW: st: graph interaction in count models

[D Ma <lrpwhn@yahoo.com>]

Thanks, Rodolphe.  I was looking at predicted "counts" in negative binomial modeling.  Also thanks for sending over the codes.  I was unable to execute it for the following step:

. drawnorm b1-b6, n(10000) means(e(b)) cov(e(V)) clear
conformability error
r(503);

May I know how to fix it?  STATA explained that this was due to matrix error (r(503)).

Best regards,

Dali




----- Original Message ----
From: Rodolphe Desbordes <rodolphe.desbordes@strath.ac.uk>
To: "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Sent: Thu, April 1, 2010 11:35:19 AM
Subject: RE: AW: st: graph interaction in count models

Dali,

Are you looking at the impact on predicted "probabilities" or on predicted "values"?

Rodolphe

PS: I think that what I suggested in an earlier answer could fit your needs...

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Martin Weiss
Sent: jeudi 1 avril 2010 16:17
To: statalist@hsphsun2.harvard.edu
Subject: AW: AW: st: graph interaction in count models


<>

" I am using STATA 10."


Mind the FAQ, then... Also, the recent
http://www.stata.com/statalist/archive/2010-04/msg00022.html



HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von D Ma
Gesendet: Donnerstag, 1. April 2010 17:10
An: statalist@hsphsun2.harvard.edu
Betreff: Re: AW: st: graph interaction in count models

Thanks, Martin.  I am using STATA 10.

Dali



----- Original Message ----
From: Martin Weiss <martin.weiss1@gmx.de>
To: statalist@hsphsun2.harvard.edu
Sent: Thu, April 1, 2010 10:38:09 AM
Subject: AW: st: graph interaction in count models


<>

"(I also don't know why there were question marks ?? in your codes)"


Those would be wildcards, denoting one character each. See [U], sect.
11.4.1.

Which -version- of Stata do you use?




HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von D Ma
Gesendet: Donnerstag, 1. April 2010 16:35
An: statalist@hsphsun2.harvard.edu
Betreff: Re: st: graph interaction in count models

Hi Maarten,

Thanks for the advice.  It looks like STATA cannot finish the programming
when it involves things like c.grade or c.tenure##c (I also don't know why
there were question marks ?? in your codes).  Could you please resend,
possibly in a format like .pdf?   In addition, suppose x2 moderates the
effect of x1 on y, I am looking the the differences of the predicted
probabilities in three scenarios: (1) -1 SD(x2), mean(x2), and +1 SD(x2).
Thanks!

Best regards,

Dali



----- Original Message ----
From: Maarten buis <maartenbuis@yahoo.co.uk>
To: statalist@hsphsun2.harvard.edu
Sent: Thu, April 1, 2010 4:12:05 AM
Subject: Re: st: graph interaction in count models

--- On Wed, 31/3/10, D Ma wrote:
> I am trying to graph an interaction between two continuous
> covariates in a count model (xtgee y x1 x2 x1*x2 ...,
> family(nb) link(log) vce(robust) nolog).  Do you have
> any suggestions as to how draw such a graph?  Thanks!

*------------------ begin example --------------------
webuse nlswork, clear
xtset idcode year
gen black = race == 2 if inlist(race, 1, 2)

xtgee wks_work c.tenure##c.grade south black, ///
      family(nb) link(log)

preserve
replace south = 0
replace black = 0
keep if e(sample)
bys grade: keep if _n == 1
expand 5
drop tenure
bys grade: gen tenure = (_n -1)*5
predict wks_hat
separate wks_hat, by(tenure)
twoway line wks_hat? wks_hat?? grade, sort
restore
*--------------------- end example ------------------
(For more on examples I sent to the Statalist see:
http://www.maartenbuis.nl/example_faq )

Hope this helps,
Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
--------------------------




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