# Re: st: how to access e(b) and e(V)

 From Philomela@gmx.net To statalist@hsphsun2.harvard.edu Subject Re: st: how to access e(b) and e(V) Date Tue, 20 Oct 2009 13:03:21 +0200

```Okay, so i try to describe what i want to do:
Actually i would like to come up with a linear demand function like that:
Consumption= constant+ beta_1*Price+beta_2*Income+ ...
and a loglog demand function.
I used the spreadheet programm and manually calculated Consumption for various prices and got the two demand functions from that, but unfortunatly, due to the log transformation i have the following problem:
exp(E(ln(Consumption))) is not equal to E(Consumption).
I thought more precise estimates would help-but as it turned out now- they don't.
So, can I  estimate the consumption for different prices directly in Stata to get the demand functions?
Then, I should be able to deal with the retransformation bias  as suggested in Cameron&Trivedi(2009):Microeconometrics using Stata.

Thank you very much!
Philomela

-------- Original-Nachricht --------
> Datum: Tue, 20 Oct 2009 02:41:38 -0700 (PDT)
> Von: Maarten buis <maartenbuis@yahoo.co.uk>
> An: statalist@hsphsun2.harvard.edu
> Betreff: Re: st: how to access e(b) and e(V)

> --- On Tue, 20/10/09, Philomela@gmx.net wrote:
> > I would like to export the coefficient matrix and the
> > variance covariance matrix into excel to do some
> > calculations-i need very exact values, so i can't use the
> > output. Where does Stata store these matrices and how can I
> > access them?
>
> With any transfer between programs you are going to loose
> some reproducability of your analysis. In this case, where
> you want to manipulate a matrix, there is no good reason
> for moving away from Stata. So, tell us what you want to
> do, and we will tell you how to do it in Stata.
>
> Having said that, the matrices e(b) and e(V) are stored in
> working memory, so if you want to access them in another
> program you will have to store them. You can use programs
> like : Michael Blasnik's and Ben Jann's -mat2txt- for that.
> To install that type in Stata -ssc install mat2txt-.
>
> 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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