Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: st: geometric means
From
Nick Cox <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: geometric means
Date
Wed, 12 Jun 2013 08:34:34 +0100
There's an -egen- function -gmean()- in -egenmore- (SSC), but the
problem yields also to elementary mathematics and official Stata:
sysuse auto
egen gmean = mean(ln(mpg)), by(rep78)
replace gmean = exp(gmean)
Note that you can't take this further and go
egen gmean2 = exp(mean(ln(mpg))), by(rep78)
because -egen- expects to see an -egen- function on the right-hand
size and -exp()- is not an -egen- function. Why then is the first code
OK? Because the -egen- function -mean()- can work on an expression and
a call to a Stata function is fine.
The overloading of the word "function" needs a little care here.
-egen- functions are those documented under -egen-. Stata functions
are documented under -functions-. There is sometimes scope to use
Stata functions _inside_ calls to -egen- functions, as here. -egen-
functions cannot be used outside -egen- in any circumstances.
Nick
[email protected]
On 11 June 2013 12:42, Nick Cox <[email protected]> wrote:
> Check out -egen-.
>
> Nick
>
>
> On 11 Jun 2013, at 10:35, Abu Camara <[email protected]> wrote:
>
>> Hi Stata list,
>>
>> I want to compute geometric means by year (time series) for a list of
>> countries with Stata's "ameans" command.
>> BY and OVER are not supported by ameans.
*
* 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/