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


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Testing for a contiguous subset of observations?
Date   Fri, 30 Nov 2007 12:01:59 -0000

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 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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