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st: RE: Query re -sortpreserve-

From   Roger Newson <>
Subject   st: RE: Query re -sortpreserve-
Date   Fri, 20 Jun 2003 18:12:22 +0100

Fellow Statalisters (especially those in charge of the [P] manual)

Thanks to Patrick Joly for pointing out this important typo in -[P] sortpreserve-. I have inserted the underscores in the program I am working on, and it works fine now.

Another useful point not mentioned in -[P] sortpreserve- is that -sortpreserve- preserves not only the original sorting order of the observations but also the value returned by the -sortedby- extended macro function. This is a good reason for using -sortpreserve-, instead of attempting to sort the data back into the original order manually by creating your own -tempvar-, setting it to _n and sorting by your -tempvar- at the end. Thanks again to Patrick for informing me privately on this point.

Best wishes


At 12:02 20/06/03 -0400, Patrick Joly wrote:

Roger Newson
> I am trying to use -sortpreserve- in Stata 7 and Stata 8
> under Windows
> 98/SE. However, there is one problem. My -sortpreserve-
> programs do not
> seem to be generating a -`sortindex'- temporary variable, as -[P]
> sortpreserve- says they should. (A simple example under Stata
> 8 is given
> below.) Why should this be the case?
> Best wishes (and thanks in advance)
> Roger
> . prog def nutz1,sortpreserve
>    1. version 8.0
>    2. disp as text "Sort index var: |`sortindex'|"
>    3. sort `sortindex'
>    4. end
> . nutz1
> Sort index var: ||
> varlist required
> r(100);

There is a typo in the manual under [P] sortpreserve (p. 402 under section
'How sortpreserve works').  A leading underscore is missing from the macro
name used for the sortpreserve variable.  References to `sortindex' should
be replaced by `_sortindex' everywhere.  The following will work:

prog def nutz1,sortpreserve
        version 8.0
        disp as text "Sort index var: |`_sortindex'|"
        sort `_sortindex'

. nutz1
Sort index var: |__000000|

Patrick Joly
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Roger Newson
Lecturer in Medical Statistics
Department of Public Health Sciences
King's College London
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42 Weston Street
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United Kingdom

Tel: 020 7848 6648 International +44 20 7848 6648
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Opinions expressed are those of the author, not the institution.

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