# Re: st: -mfx-

 From Nishant Dass To statalist@hsphsun2.harvard.edu Subject Re: st: -mfx- Date Sat, 23 Sep 2006 06:26:45 -0700 (PDT)

```Dear Maarten,

I understand that Stata doesn't know how I have transformed
but I think I didn't pose my question well.  I will try it
again.

My understanding of the different "options" in -mfx- is the
following:

When regress y on x, use "eyex" for elasticity of y w.r.t.
x
When regress y on lnx, use "eydx" for elasticity of y
w.r.t. x
When regress lny on x, use "dyex" for elasticity of y
w.r.t. x
When regress lny on lnx, use "dydx" for elasticity of y
w.r.t. x

I suppose, my question should have been posed as: is the
above interpretation correct?  A simple yes/no answer would
suffice.

Thank you very much,

Nishant

--- Maarten buis <maartenbuis@yahoo.co.uk> wrote:

> Nishant:
> Stata doesn't know that you previously logged a variable.
> It just sees
> a column in your dataset that contains numbers, what they
> mean or what
> you've done to it, Stata does not know.
> HTH,
> Maarten
>
> --- Nishant Dass <nishant_dass@yahoo.com> wrote:
> > I would like to be able to make a statement like "a 1%
> > change in lnx results in so many % change in y", so
> which
> > of the following would be correct?
> >
> >     mfx c, var(lnx) dyex
> > OR
> >     mfx c, var(lnx) dydx
> >
> > The cause of confusion is whether Stata takes the
> logarithm
> > of a variable or uses an already-"logged" variable in
> > calculating the marginal effects.  (If it simply uses
> > already-"logged" variables, then what is the use of
> options
> > other than "dydx"?)
>
>
> -----------------------------------------
> Maarten L. Buis
> Department of Social Research Methodology
> Vrije Universiteit Amsterdam
> Boelelaan 1081
> 1081 HV Amsterdam
> The Netherlands
>
> Buitenveldertselaan 3 (Metropolitan), room Z434
>
> +31 20 5986715
>
> http://home.fsw.vu.nl/m.buis/
> -----------------------------------------
>
>
>
>
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