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Re: st: Finding patterns of consecutive number


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Finding patterns of consecutive number
Date   Thu, 26 Apr 2012 02:24:04 +0100

I think of your problem as defining spells of consecutive integers, so
that a spell starts with the first observation in each panel or if the
previous value was not one fewer.

bysort id (year) : gen progress = string(test) if _n == 1 | (test -
test[_n-1] != 1)
by id : replace progress = progress[_n-1] + string(test) if missing(progress)

Dealing with spells: see also -tsspell- (SSC) or

SJ-7-2  dm0029  . . . . . . . . . . . . . . Speaking Stata: Identifying spells
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
        Q2/07   SJ 7(2):249--265                                 (no commands)
        shows how to handle spells with complete control over
        spell specification

By the way, as the putative author of -tostring-, I note that it is
overkill here. The -string()- function is all you need.

Nick

On Wed, Apr 25, 2012 at 11:47 PM, Marshall Garland
<marshall.w.garland@gmail.com> wrote:

> I have panel student testing data spanning six years. Each year, I
> have a unique student and student test level and outcome. Testing
> levels across years are not necessarily consecutive, nor are years.
> For each student, in each year, I'd like to create a variable that
> captures the longitudinal test progression for each student, in each
> year. However, for each year, I'd like the maximum consecutive test
> progression, without disruptions. This maximum test progression should
> only be calculated for consecutive years, too.
>
> I've posted my data at the end of this message, which will help
> describe my objective. For student A, in 2008/09, her test progression
> is 6543, since she had 4 consecutive years of test data. This is
> perfect. Student B, however, in 2008/09, has a test progression of
> 7643. However, I only want to record, for student B, the maximum
> consecutive test progression, which is 76 and ignore the 43. The 43
> progression will be captured in the corresponding year (2006/07).
>
> I can't figure out a way to adjust for this discontinuity. I've tried
> a number of things, including this. But, this still captures repeated
> test levels across years (student C below, in 2008/09).
>
> Thanks for help in advance.
>
> Cheers,
>
> -mwg
>
> /****************************************************
> bys research_id: gen test_t=d.test_level_2
> bys research_id: egen max_test_t=max(test_t)
>
> ///group creation for consecutive runs
> forvalues i=0/6 {
>        gen group_`i'=.
>        bys research_i (sch_yr): replace group_`i'=test_level_2[_n-`i'] if
> max_test_t==1 & test_t==1
>        tostring group_`i', replace
>        replace group_`i'="" if group_`i'=="."
> }
>
> egen group_ty_cons=concat(group_0- group_6)
> tab group_ty_cons
> /**************************************************************
>
> Here's my data:
> student year    test_level      progression
> A       2005/06 3
> A       2006/07 4       43
> A       2007/08 5       543
> A       2008/09 6       6543
> B       2005/06 3
> B       2006/07 4       43
> B       2007/08 6       643
> B       2008/09 7       7643
> C       2005/06 6
> C       2006/07 7       76
> C       2007/08 8       876
> C       2008/09 8       8876

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