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Re: st: What is EGEN_Varname and EGEN_SVarname ?
From
Daniel Feenberg <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: What is EGEN_Varname and EGEN_SVarname ?
Date
Tue, 31 Jul 2012 10:05:52 -0400 (EDT)
On Tue, 31 Jul 2012, Nick Cox wrote:
It's documented. See help on macro extended functions and the corresponding
manual entry. That is accessible by -help extended fcn-.
Can you explain further? In the referenced help entry the colon operator
appears only in the context of a -local- or -global- statement. In your
example there is no such keyword, and the macro name is also missing. I
suppose the colon operator defines a temporary macro but more explicit
documentation would be welcome.
daniel feenberg
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:[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:[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:[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:
advance my understanding of programming in Stata? Why are some folks
allowed
Nick
I don't understand your line of thought ... you actually want me NOT
to
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 ?
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the Funds is not suitable for all investors. No representation is made
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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. Al!
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or accuracy and are subject to change without notice.
Any comments or statements made herein do not necessarily reflect those of
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will make any profit at all or will be able to avoid incurring substantial
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