Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

Re: st: RE: Classifying Subjects


From   Raphael Fraser <raphael.fraser@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: Classifying Subjects
Date   Tue, 18 Oct 2005 12:22:58 -0500

Yes, gaps do exist in the data since some patients did not turn up for
their yearly test while others may have turn up three times for the
year.

> In addition, it seems possible in principle that
> an individual could be assigned to two or more
> classes according to different parts of their history.

This is true. Therefore if a patient is classed as minimal, sustained
and heavy, the latter is chosen. If another is assigned minimal and
sustained then sustained is chosen.

On 10/18/05, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> Your example indicates that gaps may exist in the data.
> Subject 31 was not measured in various years e.g. 1987,
> 1988. Thus if you want classification according to
> consecutive years you need to specify how missing
> [meaning, not present in the data] values are to be
> treated. Do you mean just consecutive tests?
>
> In addition, it seems possible in principle that
> an individual could be assigned to two or more
> classes according to different parts of their history.
>
> So, I am not clear that writing specific code is
> the best answer to you until these ambiguities are
> resolved. But if you go
>
> . bysort id (dot) : gen t = _n
> . tsset id t
>
> you can look for spells in your data according to
> your stated criteria. The user-written
> program -tsspell- from SSC can be then used. It has
> a fairly detailed help file.
>
> Nick
> n.j.cox@durham.ac.uk
>
> Raphael Fraser
>
> > I have a longitudinal data set that contains nearly 500 patients. All
> > patients were tested at these times dot (date of test) for the level
> > of protein in the blood; the result being 0 (no protein) T (trace
> > amounts of protein), 1, 2, 3 or 4. I would like to classify these
> > subjects based on the criteria below:
> >
> > "Minimal" if protein is T on at least 2 out of 3 consecutive years.
> > "Sustained" if the result is minimal and lasts 3 years or more.
> > "Heavy" if sustained with protein  2 or greater lasting 3
> > years or more.
> >
> > id            dot       protein
> > 31    15mar1985       T
> > 31    14mar1986       0
> > 31    15mar1989       T
> > 31    15mar1990       T
> > 31    15mar1991       T
> > 31    15mar1993       0
> > 31    18feb1994        T
> > 31    07jun1995        0
> > 31    23aug1996       1
> > 31    10may1999      T
>
> *
> *   For searches and help try:
> *   http://www.stata.com/support/faqs/res/findit.html
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index