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From |
K Jensen <k.x.jensen@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Analysing longitudinal data |

Date |
Tue, 26 Feb 2013 16:12:01 +0000 |

Thanks Nick. As ever that is very helpful. Kind regards Karin On 26 February 2013 15:39, Nick Cox <njcoxstata@gmail.com> wrote: > I don't think any programming is needed here at all, just a few > commands issued in a do-file or interactively. > > Your first two questions are of the form > > {count|average} in moving time interval > > and both are addressed in moderate detail within > > SJ-7-3 pr0033 . . . . . . . . . . . . . . Stata tip 51: Events in intervals > . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox > Q3/07 SJ 7(3):440--443 (no commands) > tip for counting or summarizing irregularly spaced > events in intervals > > http://www.stata-journal.com/sjpdf.html?articlenum=pr0033 > > The last has been discussed in various places, but rather than > references here is some sample code. > > gen NotWanted = (value < 1) | missing(value) > bysort ID (NotWanted Date) : gen TimeSinceLast = Date - Date[_n-1] if > !NotWanted > > The logic looks a little contrived, but the idea is to get a sort > order that looks like this, so that the time since the > last previous event is just the current date minus the previous date. > For individual, there will be only one such date, > 30/04/2011, for which the answer will be 2 days. The answer for the > first will be missing. > > 1 1.5 28/04/2011 > 1 1.3 30/04/2011 > 1 0.6 02/03/2010 > 1 0.6 24/05/2010 > 1 0.6 16/08/2010 > 1 0.6 10/11/2010 > 1 0.9 09/02/2011 > 1 0.7 01/05/2011 > 1 0.6 03/05/2011 > 1 0.6 09/05/2011 > > Once you have values in a variable, -summarize- gives you the mean. > > Nick > > On Tue, Feb 26, 2013 at 3:18 PM, K Jensen <k.x.jensen@gmail.com> wrote: > >> I have a dataset that looks like the sample I have pasted in at the >> end of this message, with repeated measures over time on the same >> individuals. >> >> I would like to answer questions like: >> When a value was over 1, how many were measured again within the next >> week? How many of those were also over 1? >> What was the average interval between a value being over 1 and the >> next value for that individual? >> >> How would I go about programming this in Stata? >> >> Thankyou >> >> Karin >> >> ID Value Date >> 1 0.6 02/03/2010 >> 1 0.6 24/05/2010 >> 1 0.6 16/08/2010 >> 1 0.6 10/11/2010 >> 1 0.9 09/02/2011 >> 1 0.7 01/05/2011 >> 1 1.5 28/04/2011 >> 1 1.3 30/04/2011 >> 1 0.6 03/05/2011 >> 1 0.6 09/05/2011 >> 2 0.6 14/04/2009 >> 2 0.7 23/07/2009 >> 2 0.6 16/11/2009 >> 2 0.6 29/12/2009 >> 2 0.6 30/03/2010 >> 2 0.9 01/07/2010 >> 2 1.2 27/09/2010 >> 2 0.7 12/10/2010 >> 2 0.7 26/10/2010 >> 2 0.8 25/03/2011 >> 3 0.3 21/01/2009 >> 3 0.3 05/11/2009 >> 3 0.1 01/03/2010 >> 3 0.2 24/05/2010 >> 3 0.2 18/08/2010 >> 4 0.9 16/02/2010 >> 4 1.0 01/03/2010 >> 4 0.9 12/03/2010 >> 4 1.1 25/03/2010 >> 4 0.5 01/06/2010 >> 4 0.4 31/08/2010 >> 4 0.6 30/11/2010 >> 4 0.6 19/04/2011 > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Analysing longitudinal data***From:*K Jensen <k.x.jensen@gmail.com>

**Re: st: Analysing longitudinal data***From:*Nick Cox <njcoxstata@gmail.com>

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