RE: st: -collapsetofile-

[Andrew Maurer <Andrew.Maurer@qrm.com>]

Thanks for the reference, David.

Looking at xcollapse.do, it internally does a preserve/save/restore. The whole idea of -collapsetofile- is to save the data without doing a preserve/restore. It looks like the intended purpose of -xcollapse- is to add features to collapse, while the purpose of -collapsetofile- is to save a file faster. (-collapsetofile-, at the moment, does far less then collapse - I still need to spend some time reading through the syntax-parsing portion of collapse to allow syntax like (sum) x1 = y x2 = z...)

It looks like I need a RePEc account to post to SSC, if I'm understanding this. I'm looking into it now.

Andrew Maurer 

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: Friday, February 28, 2014 12:47 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: -collapsetofile-

Using SSC as a medium for distributing user-written programs is naturally entirely optional for user-programmers.

It is however I think germane that SSC requires provision of help files as part of a minimum standard for inclusion of packages.

Similarly, providing help files would help people to understand exactly what these programs do and help Andrew get good feedback from anyone interested.

(If I am missing the help files, please do flag where they are.)

Nick
njcoxstata@gmail.com


On 28 February 2014 18:24, Jorge Eduardo Pérez Pérez <jorge_perez@brown.edu> wrote:
> Thanks Andrew, this looks useful.
>
> Why not submit the code to SSC to make it easier for users to install 
> this directly from Stata?
>
>
> --------------------------------------------
> Jorge Eduardo Pérez Pérez
> Graduate Student
> Department of Economics
> Brown University
>
>
> On Fri, Feb 28, 2014 at 1:19 PM, Nick Cox <njcoxstata@gmail.com> wrote:
>> -save- is part of the executable
>>
>> . which save
>> built-in command:  save
>>
>> and so its code is not accessible to users.
>>
>> Nick
>> njcoxstata@gmail.com
>>
>>
>> On 28 February 2014 18:06, Andrew Maurer <Andrew.Maurer@qrm.com> wrote:
>>> Hi Statalist,
>>>
>>> I've written a pair of program -collapsetofile- and -recover- to allow users to "collapse" data to a file without destroying the dataset like -collapse- does. I don't know if anyone else will have use for this, but it will save me a lot of computer time when dealing with large datasets. I would be very interested if anyone has any input or comments on how to improve coding efficiency / style (the code is still a bit rough).
>>>
>>> ado file (collapsetofile.ado): http://codepad.org/DcwtvDEb ado file 
>>> (recover.ado) : http://codepad.org/csZhQvb0 sthlp file 
>>> (collapsetofile.sthlp): http://codepad.org/AsKC79uK
>>>
>>> The biggest improvement would come from being able to save directly to a .dta. I assume that this would require either:
>>> 1) looking at the format/header/footer of stata dtas in clear text 
>>> and fwrite()'ing it from mata, and/or
>>> 2) looking at the source for a command like save and just copying 
>>> that (is the source for -save- available?)
>>>
>>> Before writing this I found myself waiting for hours when graphing summary statistics of large datasets with sequences of:
>>>
>>> use fulldata // this could be >10gb
>>> preserve
>>> collapse (sum) thisvar thatvar, by(byvar1 byvar2) ... some data 
>>> manipulation twoway line...
>>> restore
>>>
>>> preserve
>>> collapse (sum) anothervar yetanothervar, by(byvar3) ... some data 
>>> manipulation twoway line...
>>> restore
>>>
>>> ...
>>>
>>> preserve
>>> collapse (sum) more vars, by(byvar10) ... some data manipulation 
>>> twoway line...
>>> restore
>>>
>>> For a 20gb dataset with 10 graphs, that makes 10 preserves/restores * 20gb = 200gb written/read to disk. -collapsetofile- writes just the collapsed data to be graphed to a file with no other disk reads/writes:
>>>
>>> use fulldata
>>> collapsetofile (sum) thisvar thatvar using dataforgraph1, by(byvar1 
>>> byvar2) collapsetofile (sum) anothervar yetanothervar dataforgraph2, 
>>> by(byvar3) ...
>>> collapsetofile (sum) more vars, by(byvar10)
>>>
>>> recover dataforgraph1, clear
>>> ... some data manipulation
>>> twoway line...
>>> ...
>>> recover dataforgraph2, clear
>>> ... some data manipulation
>>> twoway line...
>>> ...
>>>
>>> Thanks to Nick Cox for mentioning the importance of saving characteristics/metadata with the dataset.
>>> Thanks to Sergiy Radyakin for making me realize that I could never write a mata program that would compute stats "by" variables as fast as stata's -_mean- in -collapse-, since stata's built-in C code can take advantage of parallelization, while mata code cannot.
>>
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