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From |
BW Wheeler <ben.wheeler@bristol.ac.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
RE: st: Testing for a contiguous subset of observations? |

Date |
Fri, 30 Nov 2007 12:18:23 -0000 |

Thanks Maarten & Nick -

Nick you are right, Maarten's method produces too many missing values; I should have specified that there would be multiple spells of zeros.

I guess 'spells' was the magic search word that I was missing! tsspell and the references you mention look like they'll do the job.

Thanks a lot

Ben

tsspell and the associated material looks like it will do the job -

--On 30 November 2007 12:01 +0000 Nick Cox <n.j.cox@durham.ac.uk> wrote:

This lumps together all the zeros for each -id- regardless of when they occurred. That is valid if there is at most one spell of zeros for each -id-. Otherwise I don't think it matches the problem. Nick n.j.cox@durham.ac.uk Maarten buis bys id (observation) : gen zero = Activity == 0 bys id zero (observation) : gen nzero = _N if zero == 0 replace nzero = 0 if nzero == . gen activity2 = activity if nzero < 60 & nzero --- BW Wheeler <ben.wheeler@bristol.ac.uk> wrote:I'm having trouble figuring out a solution to this data management problem, and have exhausted all books and findit (partly as it's hard to know what to search for)! I have time series data captured from accelerometers, with an observation of 'activity counts' logged every 10 seconds for several days for each individual. If the number of counts is zero continuouslyfor any period of 10 minutes or more (i.e. 60+ observations), we need to assume that the accelerometer was not being worn, and to treat these zeros as missing. So, my data look something like this: Observation Date Time Activity 1 13/05/2006 15:20:00 230 2 13/05/2006 15:20:10 215 3 13/05/2006 15:20:20 0 4 13/05/2006 15:20:30 0 5 13/05/2006 15:20:40 0 ... Does anyone have any ideas of how I can replace the 'Activity' value with missing, if that value is a zero in the midst of a continuous series of 60+ zeros?* * 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/

---------------------- Ben Wheeler Research Fellow Department of Social Medicine, University of Bristol & South West Public Health Observatory ben.wheeler@bristol.ac.uk * * 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/

**References**:**RE: st: Testing for a contiguous subset of observations?***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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