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st: New version of -expgen- on SSC

From   Roger Newson <>
To   "" <>, "" <>
Subject   st: New version of -expgen- on SSC
Date   Wed, 29 Dec 2010 15:00:49 +0000

Thanks to the very prompt and helpful services of Kit Baum, a new version of the -expgen- package (described as below on my website) is now available for download from SSC. In Stata, use the -ssc- command to do this, or -adoupdate- if you already have an old version of -expgen-.

The -expgen- package is described as below on my website. The new version recognizes the missing values ._ and .a to .z (as well as the standard missing value .) as being missing, for the purposes of the -missing- option. It also generates the -oldseq()- output variable initially as a -long- variable, and not as a -int- variable as the old version did, before compressing the -oldseq()- output variable if possible. I would like to thank Luciano Laveccia of the Banca d'Italia for alerting me about this horrible bug, which can cause problems of precision loss with large datasets.

Best wishes


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
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Web page:
Departmental Web page:

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

package expgen from

      expgen: Duplicate observations and add generated variables

      The program expgen is an extended version of expand. It replaces each
observation in the current dataset with multiple copies of the observation, sorted in the order of the original observations. It can also generate new
      variables, including a variable containing the sequential order of a
duplicate observation in the set of duplicate observations from the same original observation (so that if the old observation has k duplicates, then these duplicates are numbered from 1 to k in the new variable). expgen is useful if the user has a dataset of repeated measures. For instance, in a
      medical setting, the original dataset may contain one observation per
patient, and multiple variables containing repeated measures on the same patient, and the user may want to expand the original dataset into a new
      dataset, with one observation per repeated measure.

      Author: Roger Newson
      Distribution-Date: 29december2010
      Stata-Version: 10

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