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Re: st: RE: local variables and running do files


From   Abhimanyu Arora <abhimanyu.arora1987@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: local variables and running do files
Date   Sat, 29 Oct 2011 14:56:16 +0200

Thanks very much, Nick, for the illuminating post. These nuggets from
experience indeed help in deepening our understanding.
Best regards
Abhimanyu




On Sat, Oct 29, 2011 at 2:36 PM, Nick Cox <njcoxstata@gmail.com> wrote:
> This is correct, and was pointed out earlier in the thread by Jorge
> Eduardo Pérez Pérez and underlined by Matthew White.
>
> Indeed, you could use globals.
>
> The main objection to globals is I think one of style: it is just
> generally considered good style that all definitions in computing,
> like those in espionage or security, are on a need-to-know basis.
>
> Note that a global can have unpredictable side-effects elsewhere. This
> is naturally the consequence of it being visible everywhere. So,
> suppose you define a global; in principle you could be changing
> something used by a program you use without knowing it. The risk is in
> practice very small, but not zero.
>
> Stata users getting to grips with locals are often surprised by this
> lack of visibility of local macros, even within the same session, but
> two comments may provide some illumination.
>
> First, the name "local" is not an arbitrary jargon term, but conveys a
> key hint about what locals are.
>
> Second, if locals really were visible elsewhere you would have to
> worry about clashes between your locals and any locals defined in
> Stata programs defining commands (lots and lots of them); those in the
> programs they call, and that they call, and so on (lots and lots
> more); and those in the user-written commands you use (similar story).
> But this is not the case; otherwise the use of locals would be a
> minefield even for experienced users, let alone for beginners.
>
> Nick
>
> On Sat, Oct 29, 2011 at 1:15 PM, Abhimanyu Arora
> <abhimanyu.arora1987@gmail.com> wrote:
>
>> I guess Ana could make use of global macros for her problem (even as
>> if I recall there was an advice in statalist preferring `locals', but
>> I do not clearly recall the exact reason)
>> Cheers
>> Abhimanyu
>>
>> On Sat, Oct 29, 2011 at 3:12 AM, Nick Cox <njcoxstata@gmail.com> wrote:
>>> It's the same question. The use of a local requires its prior
>>> definition in the same locale.
>>> "Locale", although a term used elsewhere in computing, is in this
>>> context my term earlier defined in the thread.
>>>
>>> Nick
>>>
>>> On Fri, Oct 28, 2011 at 7:40 PM, Maria Ana Vitorino
>>> <vitorino@wharton.upenn.edu> wrote:
>>>> I am using Stata 11.
>>>> But in any case what if I want to run some regressions, for example:
>>>>
>>>> reg y x1 x2 x3
>>>>
>>>> is equiv to
>>>>
>>>> --regtest.do
>>>> local x "x1 x2 x3"
>>>> reg y `x'
>>>> ----
>>>>
>>>>
>>>> but if after running the first 2 lines I want to run the command " sum `x' "
>>>>  it does not work. Is there anyway around this so that I don't have to
>>>> define the local macro again?
>>>>
>>>> Thanks,
>>>> Ana
>>>>
>>>>
>>>>
>>>> On Oct 28, 2011, at 2:30 PM, Nick Cox wrote:
>>>>
>>>>> The term "local variable" is to be avoided, as explained at
>>>>>
>>>>> http://www.stata.com/statalist/archive/2008-08/msg01258.html
>>>>>
>>>>> What you are seeing is a defining feature of a local macro: it is visible
>>>>> only locally, i.e. within the locale in which it is defined, i.e. not
>>>>> visible outside the interactive session, program, do file or do file editor
>>>>> contents within which it is defined.
>>>>>
>>>>> You need to pass the contents of your local macro to the do-file as an
>>>>> argument. If you write e.g.
>>>>>
>>>>> ------------ mydo.do
>>>>> su `1'
>>>>> ------------
>>>>>
>>>>> And then go
>>>>>
>>>>> mydo "var1 var2"
>>>>>
>>>>> then the do file uses the argument you feed to it. Arguments are separated
>>>>> by spaces and bound by " ". This is all explained in the chapter(s) on
>>>>> do-files in [U], which is part of your Stata, as without declaring otherwise
>>>>> it is assumed that you are using Stata 12.
>>>>>
>>>>> Nick
>>>>> n.j.cox@durham.ac.uk
>>>>>
>>>>> Maria Ana Vitorino
>>>>>
>>>>> I would like to run a do file in batches (i.e. a few lines at a time)
>>>>> but it seems that then the local variables that I defined in the
>>>>> beginning do not carry over ...
>>>>> Any solution for this?
>>>>>
>>>>> Here is some output for a simple example so that you can better
>>>>> understand what is my issue.
>>>>>
>>>>> Thanks!!
>>>>> Ana
>>>>>
>>>>>
>>>>> . do "/var/folders/Xn/Xnl4Mq-lGR4-mNII1zm-Wk+++TI/-Tmp-//SD17268.000000"
>>>>>
>>>>> . sum
>>>>>
>>>>>    Variable |       Obs        Mean    Std. Dev.       Min        Max
>>>>> -------------+--------------------------------------------------------
>>>>>        var1 |        24        12.5    7.071068          1         24
>>>>>        var2 |        24        36.5    7.071068         25         48
>>>>>        var3 |        24        61.5 7.071068         50         73
>>>>>
>>>>> . local var "var1 var2"
>>>>>
>>>>> .
>>>>> end of do-file
>>>>>
>>>>> . do "/var/folders/Xn/Xnl4Mq-lGR4-mNII1zm-Wk+++TI/-Tmp-//SD17268.000000"
>>>>>
>>>>> . sum `var'
>>>>>
>>>>>    Variable |       Obs        Mean    Std. Dev.       Min        Max
>>>>> -------------+--------------------------------------------------------
>>>>>        var1 |        24        12.5    7.071068          1         24
>>>>>        var2 |        24        36.5    7.071068         25         48
>>>>>        var3 |        24        61.5 7.071068         50         73
>>>>>
>
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