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st: RE: Problem with stsplit and survey data that isn't


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Problem with stsplit and survey data that isn't
Date   Tue, 24 Oct 2006 14:17:53 +0100

Stata itself can help answer questions like this. 
In this case, I have knowledge of -svy- of measure 
zero, but how did I try to find out something for you? 

A first principle is that most Stata commands 
are just more Stata, and as such often fairly
intelligible even if you are not a user-programmer. 
Thus command -foo- is usually defined by -foo.ado-. 

The second principle is that -viewsource- will
show you the code: 

In this case 

. viewsource stsplit.ado 

opens a window on the code, which starts like
this. (You don't need even to work out where it
is on your system, as -viewsource- gets that
job done first.) 

*! version 2.2.4  15sep2004
program define stsplit
        version 7, missing

        if _caller() < 6 {
                ztspli_5 `0'
                exit
        }
        st_is 2 full

        if `"`_dta[st_id]'"' == "" {
                di as err /*
                */ "stsplit requires that you have previously stset an id() variable"
                exit 198
        }

        capture svyset
        if "`r(_svy)'" ~= "" {
                di as err "stsplit not allowed with survey data"
                exit 498
        }

Thus, as you surmise, -stsplit- looks for indications that
you, or whoever set up the data, have previously declared 
-svy- settings to Stata. In this case, the trail suggests 
a look at -help svyset-, which 
indicates a way to clear such settings, so the rather
drastic expedient you have outlined is not necessary at all. 

There is more on -viewsource- in a Stata Journal Tip, 

SJ-6-1  pr0022  . . . . . . . . . . . Stata tip 30: May the source be with you
        Q1/06   SJ 6(1):149--150                                 (no commands)
        tip for using viewsource to locate and view source
        code or text files

which is also reprinted in the collection of 33 Stata Tips 
available at modest price from StataCorp. 

Nick 
n.j.cox@durham.ac.uk 

Richard Atkins
 
> I've solved my problem but I don't know why and I'd like to understand
> better.
> 
> I was trying to use the stsplit command on a set of data and 
> getting an
> error message "stsplit not allowed with survey data".  
> I checked and my do file did not contain any svy... commands. I also
> checked that my data had no underscore prefixed variables 
> from any prior
> svy commands that may have been used historically so I 
> couldn't see why
> stata thought this data had been identified as survey data.  Next step
> was to save the dataset and then try again with a minimal 
> command set of
> clear, use, stset and then stsplit.  Still the same error.  Finally I
> 'keep'ed just the four variables required for these commands 
> (ageentry,
> ageexit, dead, id) and tried again and it worked.
> 
> It appears that something stored in or attached to one of the dropped
> variables identified this data as survey data. This particular dataset
> contains about 400 variables so I am reluctant to use trial 
> and error to
> identify the culprit, so can anyone tell me what might cause this?

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