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RE: Antwort: st: Fwd: exponential regression in stata


From   Nick Cox <n.j.cox@durham.ac.uk>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   RE: Antwort: st: Fwd: exponential regression in stata
Date   Wed, 19 Jan 2011 17:08:14 +0000

Absolutely not so. 

1. I've already pointed out that these (Justina's and mine) proposals are exactly the same. 

2. There is no objection in principle to using the functional form exp(a + bx) with x sometimes negative. You can see this for yourself in Stata, e.g. by 

. twoway function exp(1 + 2*x) , ra(-2 2) || function exp(1 - 2*x), ra(2 -2)

Whether it is a good choice for your data is a different question. 

I suggest a crash (revision) course in exponential and logarithmic functions! 

Nick 
n.j.cox@durham.ac.uk 

Bastian Steingros

hi Justian, the point is, that some of my x var's are negative, so ln would not work. nick cox suggest to consider transforming the y var's only...

Justina Fischer <JFischer@diw.de>
 
> You might consider transforming your model prior to estimating, e.g. taking
> the  log (ln) on both sides.

> Von: "Bastian Steingros" <Steingros@gmx.de>
 
> I want to run a exp. regression in stata. But I have not found any
> instructions in the help options. do you have any ideas what to enter in
> stata to obtain such a regression model?
> 
> I mean by exp. function something like : y=0,343 * e^(22,33*x)
> 
> [my data set has 1 dep. var. and 3 indep. var.'s --> is such a model also
> possible for 3 x-var's?]

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