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


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Testing for a contiguous subset of observations?
Date   Fri, 30 Nov 2007 11:58:43 -0000

Some people call such problems "spell" problems. 
Others might talk of runs. 

Either way, discussions and tools exist. -tsspell- from SSC 
and the discussion in 

SJ-7-2  dm0029  . . . . . . . . . . . . . . Speaking Stata: Identifying
spells
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N.
J. Cox
        Q2/07   SJ 7(2):249--265                                 (no
commands)
        shows how to handle spells with complete control over
        spell specification

apply. See the help file for -tsspell- which includes several examples. 

Nick 
n.j.cox@durham.ac.uk 

BW Wheeler

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 continuously
for 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?


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