Re: st: Unpublicized changes to Saved Results for -reshape-

[Roger Newson <r.newson@imperial.ac.uk>]

Thanks to Alan for clarifying the position re -reshape-.

One further query. The returned result -_dta[__JValLab]- still looks 
potentially useful to users, even though it is undocumented. And, from 
looking inside -reshape.ado-, it seems to me that it is used to make the 
-reshape wide- command reversible by using -reshape long-. Is this 
result likely to stay, or is it likely to disappear at any time without 
warning?

Best wishes

Roger


Roger B Newson BSc MSc DPhil
Lecturer in Medical Statistics
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute
Imperial College London
Royal Brompton Campus
Room 33, Emmanuel Kaye Building
1B Manresa Road
London SW3 6LR
UNITED KINGDOM
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Email: r.newson@imperial.ac.uk
Web page: http://www.imperial.ac.uk/nhli/r.newson/
Departmental Web page:
http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/

Opinions expressed are those of the author, not of the institution.

On 26/04/2010 20:53, Alan Riley wrote:
> Roger Newson (r.newson@imperial.ac.uk) asked about saved results
> after -reshape-:
>
> > I have noticed some recent unpublicized changes to the Saved Results for
> > the -reshape- command (see -help reshape-). In my Stata 11.0 (which I
> > updated today to the sub-version dated 20 April 2010), the -reshape-
> > command produces a selection of returned dataset characteristics that is
> > different from the selection advertized in -help reshape-. In
> > particular, if I use -reshape wide-, then the advertized result
> > -_dta[ReS_jv]- (containing the values of the variable specified by the
> > -j()- option) is no longer stored. On the other hand, if the variable
> > specified by the -j()- option had a value label, then -reshape- saves
> > the unpublicized results -_dta[__JValLabName]-, containing the name of
> > the value label, and -_dta[__JValLab]-, containing the values of the
> > -j()- variable alternating with the corresponding value labels.
> >
> > The changes have the appearance of being work in progress, and, when
> > complete, will probably extend the capabilities of -reshape- in ways
> > which will be useful to users like me, who frequently use -reshape- to
> > produce tables with multiple columns of confidence intervals (see
> > Section 4.4 of Newson, 2003). However, the selection of results seems
> > currently to be unstable, implying that it is currently not a good idea
> > for users to use these saved results in their own programs. Are these
> > results likely to stabilize soon? If not, then it is probably a good
> > idea for users to avoid using these results for the time being, and to
> > make their own solutions. (I currently often use Ben Jann's very useful
> > -labelsof- package, downloadable from SSC, when I want to store values
> > and labels of -j()- variables when using -reshape wide-.)
>
> The saved results from -reshape- are not a work in progress and
> should be stable.  We are unable to reproduce the behavior Roger
> reported of the characteristic _dta[ReS_jv] not being stored after
> -reshape wide-.
>
> Roger may have noticed this because _dta[ReS_jv] is only stored if the
> optional 'values' portion of the -j()- option is filled in.  If -j()- is
> used with simply a variable name, with no values specified, then
> _dta[ReS_jv] will not be stored.  This behavior has not changed and is
> documented, if tersely, in both -help reshape- and [R] reshape.
>
> Roger also notes that -reshape- "produces a selection of returned dataset
> characteristics that is different from the selection advertized in -help
> reshape-".  I believe Roger is referring to some returned results that are not
> documented.  These are intentional and are needed for -reshape-'s own tracking
> purposes to be able to successfully convert between wide and long forms of the
> data.  These characteristics are intentionally not documented, however, as
> they were not intended to be consumed by end users.
>
>
> --Alan
> (ariley@stata.com)
>
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