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# Re: st: Log Transformation of Variable

 From Chris Hajzler To statalist@hsphsun2.harvard.edu Subject Re: st: Log Transformation of Variable Date Mon, 28 Feb 2011 07:57:45 +1300

```When you refer to "multiplying" the variable by the listed functions,
do you simply mean you would like to transform that variable by the
specified (nested) function?  If just the simple transformation is
what you want, then your problem is that you have a function of
different functions of the variable, with three transformations of the
variable to be done separately in steps, rather than one single
transformation that is already built into stata.

If I am understanding what it is you are trying to do, you would want
to do something like the following: If y is the variable you would
like to transform,

gen neg_log_y = -log(y)
gen neg_exp_y = -exp(y)
gen transformed_y = neg_log_y + neg_exp_y

Hope this helps.

Chris

On Mon, Feb 28, 2011 at 12:28 AM, Gordon Hughes <G.A.Hughes@ed.ac.uk> wrote:
> It is completely unclear to me - probably other readers - what you are
> trying to do mathematically.  You refer to "multiplying" by (-log -e) but
> log is a function while -log(x)-e is a composite transformation of x.
>  Equally there is no mathematical operator that corresponds to [-log-e](x).
>  Get the mathematics right and Stata can help, but it is not designed to
> sort out nonsense mathematics.
>
> Gordon Hughes
> g.a.hughes@ed.ac.uk
>
>> ------------------------------
>>
>> Date: Sat, 26 Feb 2011 12:04:48 -0500
>> From: Melissa King <melissakng@gmail.com>
>> Subject: st: Log Transformation of Variable
>>
>> Good Morning,
>>
>> I have a dataset that I would like to transform by multiplying the
>> dependent variables by -log - e, or in other words, the negative
>> logarithm minus its base. Despite searching this forum and the
>> Internet, I have been unable to find any information on how to "tell"
>> Stata to do this. I am able to transform my variable by multiplying it
>> by negative log:
>>
>> generate transformed_dep_variable = -log(dep_variable)
>>
>> However, Stata errors out when I try to communicate -(log+e), because
>> it no longer recognizes log as a function when I type this in:
>>
>> generate transformed_dep_variable = -(log+e)(dep_variable)
>>
>> Do any long-time Stata users have any suggestions?
>>
>>
>> All best,
>>
>> Melissa King
>
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