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RE: st: What is EGEN_Varname and EGEN_SVarname ?
From
Pradipto Banerjee <[email protected]>
To
"[email protected]" <[email protected]>
Subject
RE: st: What is EGEN_Varname and EGEN_SVarname ?
Date
Tue, 31 Jul 2012 08:04:57 -0500
No, it's not!
What is documented is
{local | global} macname : word # of string
i.e. that we can define macname to hold a word from a string
What is not documented is that we can create a local variable on the fly such as
`: word # of string'
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Nick Cox
Sent: Tuesday, July 31, 2012 9:00 AM
To: [email protected]
Subject: Re: st: What is EGEN_Varname and EGEN_SVarname ?
It's documented. See help on macro extended functions and the
corresponding manual entry. That is accessible by -help extended fcn-.
Nick
On 31 Jul 2012, at 13:47, Pradipto Banerjee <[email protected]
> wrote:
> Nick, That's very interesting. I wasn't aware that this kind of
> usage of ":" is possible. It's another undocumented feature.
>
>
> -----Original Message-----
> From: [email protected] [mailto:owner-
> [email protected]] On Behalf Of Nick Winter
> Sent: Tuesday, July 31, 2012 8:41 AM
> To: [email protected]
> Subject: Re: st: What is EGEN_Varname and EGEN_SVarname ?
>
> Not that this is the advice you are looking for, but I tend to solve
> this sort of problem like this:
>
> local newvars test1 test2
> local oldvars price mpg
>
> forval i=1/`: word count `newvars'' {
> egen `: word `i' of `newvars'' = sum(`: word `i' of oldvars'')
> }
>
> or
>
> local newvars test1 test2
> local ptiles 10 90
>
> forval i=1/`: word count `newvars'' {
> egen `: word `i' of `newvars'' = pctile(price), p(`: word `i' of
> ptiles'')
> }
>
>
>
> s
>
>
> On 7/30/2012 6:50 PM, Pradipto Banerjee wrote:
>> In case, it helps why I was asking about EGEN_Varname and
>> EGEN_SVarname, this is a command of the-egenmult- code I have
>> written that repeatedly calls -egen-. The way it works is as follows:
>>
>> . sysuse auto, clear
>>
>> Example # 1
>> . by foreign, sort: egenmult {test1 test2} = sum({price mpg})
>>
>> It works equivalently as:
>>
>> . sort foreign
>> . by foreign: egen test1 = sum(price)
>> . by foreign: egen test2 = sum(mpg)
>>
>> Example # 2
>> . drop test1 test2
>> . by foreign, sort: egenmult float {test1 test2} = pctile(price), p
>> ({10 90})
>>
>> It works equivalent as:
>>
>> . sort foreign
>> . by foreign: egen float test1 = pctile(price),p(10)
>> . by foreign: egen float test2 = pctile(price),p(90)
>>
>> I've been trying to see if I'm missing anything in the code below.
>> Thanks.
>>
>> -----
>> program define egenmult, byable(onecall) sortpreserve
>> local fullexp `0'
>> gettoken type 0 : 0, parse(" ")
>> local restexp `"`0'"'
>>
>> /* gen a list of all possible types */
>> local types "byte int long float double"
>> forvalues i=1(1)244 {
>> local types "`types' str`i'"
>> }
>> local typegiven strpos(`"`types'"',`"`type'"')
>> if `typegiven' > 0 local fullexp `restexp'
>> else local type
>>
>> /* get the number & locations of the { } */
>> local partexp = `"`fullexp'"'
>> local curvefnd = 0
>> local numbrak = 0
>> local allopenpos
>> local allclosepos
>> local alloptions
>> while `curvefnd' == 0 {
>> local openpos = strpos(`"`partexp'"',"{")
>> if `openpos'>0 {
>> local allopenpos `allopenpos' `openpos'
>> local closepos = strpos(`"`partexp'"',"}")
>> if `closepos' == 0 error 198
>> local allclosepos `allclosepos' `closepos'
>> local numbrak = `numbrak'+1
>> if `"`alloptions'"'=="" {
>> local newoptions = substr
>> (`"`partexp'"',`openpos'+1,`closepos'-`openpos'-1)
>> local alloptions `"`newoptions'"'
>> local numloop = wordcount
>> (`"`newoptions'"')
>> }
>> else {
>> local newoptions = substr
>> (`"`partexp'"',`openpos'+1,`closepos'-`openpos'-1)
>> if `numloop'!=wordcount
>> (`"`newoptions'"') error 198
>> local alloptions `"`alloptions'"'
>> `"`newoptions'"'
>> }
>> }
>> else {
>> local curvefnd = 1
>> }
>> local partexp = subinstr(`"`partexp'"',"{","!",1)
>> local partexp = subinstr(`"`partexp'"',"}","!",1)
>> }
>> local tollen = strlen(`"`partexp'"')
>>
>> /* recreate & run the individual commands */
>> forvalues iloop=1(1)`numloop' {
>> forvalues jbrak=1(1)`numbrak' {
>> if `jbrak'==1 {
>> local jthbrakopen : word `jbrak' of
>> `allopenpos'
>> local newexp = substr(`"`partexp'"',
>> 1,`jthbrakopen'-1)
>> local repexp : word `jbrak' of
>> `"`alloptions'"'
>> local repexp = word
>> (`"`repexp'"',`iloop')
>> local newexp = `"`newexp'"' + " " +
>> `"`repexp'"' + " "
>> }
>> else {
>> local jthbrakopen : word `jbrak' of
>> `allopenpos'
>> local jprevbrak = `jbrak'-1
>> local jprevbrakclose : word
>> `jprevbrak' of `allclosepos'
>> local newexp = `"`newexp'"' + " " +
>> substr(`"`partexp'"',`jprevbrakclose'+1,`jthbrakopen'-
>> `jprevbrakclose'-1)
>> local repexp : word `jbrak' of
>> `"`alloptions'"'
>> local repexp = word
>> (`"`repexp'"',`iloop')
>> local newexp = `"`newexp'"' + " " +
>> `"`repexp'"' + " "
>> }
>> }
>> local jprevbrakclose : word `numbrak' of
>> `allclosepos'
>> local newexp = `"`newexp'"' + substr
>> (`"`partexp'"',`jprevbrakclose'+1,`tollen'-`jprevbrakclose')
>> if _by() by `_byvars': egen `type' `newexp'
>> else egen `type' `newexp'
>> }
>>
>> end
>>
>> -----
>>
>> -----Original Message-----
>> From: [email protected] [mailto:owner-
>> [email protected]] On Behalf Of Pradipto Banerjee
>> Sent: Monday, July 30, 2012 5:25 PM
>> To: [email protected]
>> Subject: RE: st: What is EGEN_Varname and EGEN_SVarname ?
>>
>> Thanks, Billy. After reading your email, I realized that perhaps my
>> questions weren't clear. So, I thought to rewrite them:
>>
>> 1. One of the things I specifically asked was where did the -egen-
>> code figure out that it was supplied with -by- or -bysort-.
>>
>> 2. On a standalone basis, what does it mean if we use "_all" such
>> as in `"`args'"' =="_all"? I already AWARE of the usage(s) of _all
>> in -drop _all-, -program drop _all- etc. This usage of `"`args'"'
>> =="_all" is NOT documented in the programming manual!
>>
>> 3. In the -egen- code, what the following line achieve? Or intends
>> to achieve?
>>
>> local args : subinstr local args "`_sortindex'" "", all word
>>
>> 4. Regarding your comment "The global macros need to be defined so
>> they can be passed to the other functions (which is why Nick
>> explicitly mentioned that they are there because local macros would
>> not work in this context).", I was specifically asking: why do they
>> need to be passed on to other functions and why do they need to be
>> defined twice?
>>
>> 5. Yes, I have read the Programming Manual - and none of the
>> questions I have asked can be resolved using the Manual. Kit Baum's
>> book as the name suggests is an Introduction. Please let me know if
>> that book the specifically any of the questions I asked.
>
>>
>> Best.
>>
>>
>> -----Original Message-----
>> From: [email protected] [mailto:owner-
>> [email protected]] On Behalf Of William Buchanan
>> Sent: Monday, July 30, 2012 5:10 PM
>> To: [email protected]
>> Subject: RE: st: What is EGEN_Varname and EGEN_SVarname ?
>>
>> Hi Pradipto,
>>
>> I'll try to answer what I can, but it may not be much and others on
>> the list
>> would likely have much more refined/precise answers.
>>
>> 1. The lines of code:
>>
>> if _by() {
>> local byopt "by(`_byvars')"
>> local cma ","
>> }
>>
>> might be what you are looking for, but you should also read the
>> help file
>> for the -byable- option in the programming manual. This will
>> better explain
>> things.
>>
>> 2. Not sure about all of your question here, but you should
>> consider the
>> context in which this line occurs
>>
>> if `"`args'"' == "_all" | `"`args'"' == "*" {
>> version 7.0, missing
>> unab args : _all
>> local args : subinstr local args "`_sortindex'"
>> "", all
>> word
>> version 6.0, missing
>> }
>>
>> Which seems like it is parsing different ways that you could
>> include the
>> entire varlist in your dataset. And _all is used in more than just
>> -drop-.
>
>> For example, -log query _all- or -program drop _all- are other uses
>> of
>> "_all".
>>
>> 3. The global macros need to be defined so they can be passed to
>> the other
>> functions (which is why Nick explicitly mentioned that they are there
>> because local macros would not work in this context).
>>
>>
>> Have you read the programming manual for Stata yet? If not I would
>> highly
>> suggest going through that and possibly looking into other
>> resources (Kit
>> Baum's book is pretty awesome). Otherwise, you could probably just
>> as
>> easily create a work around using tempvars that you could combine
>> into a
>> single variable that is stored at the end of the routine with a loop.
>>
>> HTH,
>> Billy
>>
>>
>>
>>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of Pradipto
>> Banerjee
>> Sent: Monday, July 30, 2012 1:47 PM
>> To: [email protected]
>> Subject: RE: st: What is EGEN_Varname and EGEN_SVarname ?
>>
>> Billy,
>>
>> I'm primarily trying to understand Stata syntax within the -egen-
>> code to
>> write my "own" function rather than modify the -egen- code. Perhaps
>> you can
>> help me. For instance,
>>
>>
>> 1. How does the egen function handle the "by" part:
>>
>> . by var1: egen ...
>> . bysort var1 (var2): egen ...
>>
>> i.e., where in the egen code, does it figure out that it needs to
>> sort
>> before doing a by operation etc (i.e. where does it figure out that
>> it was
>> supplied with -by- instead of -bysort- etc). Similarly, in another
>> part of
>> the function, it's written
>>
>> . capture noisily _g`fcn' `type' `dummy' = (`args') `if' `in' /*
>> */ `cma' `byopt' `options'
>>
>> Why is the "by" part done this way?, i.e. why isn't this given as
>>
>> . capture noisily by _byvars: _g`fcn' `type' `dummy' = (`args')
>> `if' `in' ,
>> `options'
>>
>>
>> 2. In the part of the code where it is written:
>>
>> (a) . local args : subinstr local args "`_sortindex'" "", all word
>>
>> Why are we changing all instances of _sortindex as blanks? Isn't the
>> sortindex typically like __000000 (or something similar), and it
>> isn't
>> normally provided when a person is calling the egen function?
>>
>> (b) . if `"`args'"' =="_all"
>>
>> Usually, I had seen _all been used as drop _all. What does the
>> above part of
>> the code mean?
>>
>> 3. (a) Why do we need to define EGEN_SVarname and EGEN_Varname to
>> `name' and
>> _sortindex before calling the _g`fcn', AND (b) why do we need to
>> define them
>> again to Null?
>>
>> Thanks
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of William
>> Buchanan
>> Sent: Monday, July 30, 2012 1:00 PM
>> To: [email protected]
>> Subject: RE: st: What is EGEN_Varname and EGEN_SVarname ?
>>
>> Pradipto,
>>
>> Another important thing to consider, with regards to Nick's advice,
>> is that
>> he is basically trying to prevent you from making any changes to your
>> installed copy of Stata that might "break" it. If you're changing
>> the
>> global macros in the egen files then you run the risk of making a
>> change
>> that prevents egen from working correctly in the future. If you
>> wanted to
>> see what those variables are, you could do something like:
>>
>> viewsource egen.ado (copy the material in the window into the do
>> file editor
>> or another text editor of your choice)
>>
>> save your clone as myegen.ado to your personal directory (if you're
>> unsure
>> where this is you can use the -sysdir- command)
>>
>> pick the function that you were trying to modify and do the same
>> thing
>> (e.g., copy the source into a new file myconcat.ado for example).
>>
>> Now if you make a call to -myegen- make sure that you are using the
>> function
>> that you've duplicated and you can change the global macros in your
>> duplicate files.
>>
>> The point, however, is to avoid editing any of the files that are
>> native to
>> the Stata installation unless you're willing to risk making
>> potentially
>> harmful changes. Additionally, Nick also provided you with an
>> example
>> earlier illustrating how you could make the egen subroutine that
>> you were
>> interested in byable, so you could just start working with that
>> code and
>> modifying it as necessary.
>>
>> HTH,
>> Billy
>>
>>
>>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of Nick Cox
>> Sent: Monday, July 30, 2012 9:41 AM
>> To: [email protected]
>> Subject: Re: st: What is EGEN_Varname and EGEN_SVarname ?
>>
>> I am mixing explanations and advice on different levels. Feel free
>> to take
>> the explanations when correct and ignore the advice if it doesn't
>> appeal.
>> Otherwise I think Maarten's reply to you captures my attitude well.
>> It is a
>> defining characteristic of a discussion list that people aren't
>> obliged to
>> offer exactly the kind of support that posters of questions might
>> prefer.
>>
>> Nick
>>
>> On Mon, Jul 30, 2012 at 8:48 AM, Pradipto Banerjee
>> <[email protected]> wrote:
>>> Nick
>>>
>>> I don't understand your line of thought ... you actually want me NOT
>>> to
>> advance my understanding of programming in Stata? Why are some
>> folks allowed
>> to understand advanced programming and others not?
>>> Sorry to say this, but one huge negative of Stata is that there is
>>> so
>>> much
>> undocumented stuff - and for efficient programming we have to
>> repeatedly
>> rely on email lists like this.
>>>
>>> -----Original Message-----
>>> From: [email protected]
>>> [mailto:[email protected]] On Behalf Of Nick Cox
>>> Sent: Saturday, July 28, 2012 9:33 AM
>>> To: [email protected]
>>> Subject: Re: st: What is EGEN_Varname and EGEN_SVarname ?
>>>
>>> These are names of globals defined in -egen- to communicate between
>>> programs, which manifestly can't be done through locals, apart from
>>> using non-documented features. If you're following my earlier advice
>>> you will leave them in peace.
>>>
>>> Nick
>>>
>>> On 27 Jul 2012, at 16:03, Pradipto Banerjee
>>> <[email protected]
>>>> wrote:
>>>
>>>> I noticed some of the codes, e.g. _ggroup2 use EGEN_Varname and
>>>> EGEN_SVarname and recently one of the codes shared by Nick (called
>>>> ereplace) use these. What is EGEN_Varname and EGEN_SVarname ?
>>> *
>> *
>> * For searches and help try:
>> * http://www.stata.com/help.cgi?search
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>>
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>>
>> This communication is for informational purposes only. It is not
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>> to be, nor should it be construed or used as, financial, legal, tax
>> or
>> investment advice or an offer to sell, or a solicitation of any
>> offer to
>> buy, an interest in any fund advised by Ada Investment Management
>> LP, the
>> Investment advisor. Any offer or solicitation of an investment in
>> any of
>> the Funds may be made only by delivery of such Funds confidential
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>> Funds is not suitable for all investors. No representation is made
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>> Performance results are net of applicable fees, are unaudited and
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>> Any comments or statements made herein do not necessarily reflect
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>> legal, tax or investment advice or an offer to sell, or a
>> solicitation of any offer to buy, an interest in any fund advised
>> by Ada Investment Management LP, the Investment advisor. Any offer
>> or solicitation of an investment in any of the Funds may be made
>> only by delivery of such Funds confidential offering materials to
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>> that the Funds will or are likely to achieve their objectives, or
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> l f!
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>> Any comments or statements made herein do not necessarily reflect
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>> legal, tax or investment advice or an offer to sell, or a
>> solicitation of any offer to buy, an interest in any fund advised
>> by Ada Investment Management LP, the Investment advisor. Any offer
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>> that the Funds will or are likely to achieve their objectives, or
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>
>
> *
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> This communication is for informational purposes only. It is not
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> legal, tax or investment advice or an offer to sell, or a
> solicitation of any offer to buy, an interest in any fund advised by
> Ada Investment Management LP, the Investment advisor. Any offer or
> solicitation of an investment in any of the Funds may be made only
> by delivery of such Funds confidential offering materials to
> authorized prospective investors. An investment in any of the Funds
> is not suitable for all investors. No representation is made that
> the Funds will or are likely to achieve their objectives, or that
> any investor will or is likely to achieve results comparable to
> those shown, or will make any profit at all or will be able to avoid
> incurring substantial losses. Performance results are net of
> applicable fees, are unaudited and reflect reinvestment of income
> and profits. Past performance is no guarantee of future results.
> All f!
> inancial data and other information are not warranted as to
> completeness or accuracy and are subject to change without notice.
>
> Any comments or statements made herein do not necessarily reflect
> those of Ada Investment Management LP and its affiliates. This
> transmission may contain information that is confidential, legally
> privileged, and/or exempt from disclosure under applicable law. If
> you are not the intended recipient, you are hereby notified that any
> disclosure, copying, distribution, or use of the information
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This communication is for informational purposes only. It is not intended to be, nor should it be construed or used as, financial, legal, tax or investment advice or an offer to sell, or a solicitation of any offer to buy, an interest in any fund advised by Ada Investment Management LP, the Investment advisor. Any offer or solicitation of an investment in any of the Funds may be made only by delivery of such Funds confidential offering materials to authorized prospective investors. An investment in any of the Funds is not suitable for all investors. No representation is made that the Funds will or are likely to achieve their objectives, or that any investor will or is likely to achieve results comparable to those shown, or will make any profit at all or will be able to avoid incurring substantial losses. Performance results are net of applicable fees, are unaudited and reflect reinvestment of income and profits. Past performance is no guarantee of future results. All f!
inancial data and other information are not warranted as to completeness or accuracy and are subject to change without notice.
Any comments or statements made herein do not necessarily reflect those of Ada Investment Management LP and its affiliates. This transmission may contain information that is confidential, legally privileged, and/or exempt from disclosure under applicable law. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, or use of the information contained herein (including any reliance thereon) is strictly prohibited. If you received this transmission in error, please immediately contact the sender and destroy the material in its entirety, whether in electronic or hard copy format.
*
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