Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.

# Re: st: RE: Calculate confidence intervals for log-log models

 From Richard Goldstein To statalist@hsphsun2.harvard.edu Subject Re: st: RE: Calculate confidence intervals for log-log models Date Tue, 05 Mar 2013 15:33:56 -0500

```I don't know that this actually makes a lot of sense, but here is how to
do it: (1) don't use -lincom- as that is for linear combinations and
powers are not linear; (2) us -nlcom- as in

nlcom 1.1^_b[lnx]

Rich

On 3/5/13 3:26 PM, Jason Ferris wrote:
> Hi Nick,
>
> Sorry for my ambiguity.  And thank you for your response.
>
> Before, I start writing my own code to do this I will attempt to clarify.
>
> Yes I transformed both Y and X with a natural log transformation ln(y) and ln(x)
>
> I then regress lny on lnx
>
> OLS example of a result:
>
> ------------------------------------------------------------------------------
>          lny |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
> -------------+----------------------------------------------------------------
>          lnx |   2.105722   .0817271    25.77   0.000     1.942802    2.268642
>        _cons |  -3.032146   .4274653    -7.09   0.000    -3.884282   -2.180009
> ------------------------------------------------------------------------------
>
> To calculate a 10% change on lnx (with confidence intervals) when I type
> lincom 1.1^lnx - I get the message 'not possible with text'
>
> I would like to construct a table highlighting percentage changes in lny with a series of percentage changes (10,25...) in lnx
>
> Kind regards,
>
> Jason
>
> On Tue, 5 Mar 2013 12:49:28 +0000 Nick Cox <njcoxstata@gmail.com> wrote:
>
> Not really clear what you are doing but I guess that you are
> transforming first. Either way, something like
>
> _b[ln(y)]
>
> makes no sense to Stata as
>
> ln(y)
>
> can't be a variable name.
>
> I fear you need to write your own code.
>
> Nick
>
> On Tue, Mar 5, 2013 at 11:30 AM, Jason Ferris <j.ferris@uq.edu.au> wrote:
>
>> I have run a series of log-log OLS models - ln(y)=ln(x)+cons - and would like to present a table of percentage change at 10%, 25%, 50%, & 75% with corresponding changes in the confidence intervals.
>>
>> Is there a way to do this in Stata or a ado file that I could utilise.
>>
>> When trying to use lincom (.e.g., 1.1^_b[ln(x)] - I get a 'not possible with test' error.  What are the alternatives besides doing it all by hand?
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/
```