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RE: st: difference between rows
From
"Dougie Elder" <[email protected]>
To
<[email protected]>
Subject
RE: st: difference between rows
Date
Mon, 23 May 2011 13:52:46 +0100
Great - thanks Chris ... it seems obvious now !
Cheers
Dougie
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Chris Parker
Sent: 20 May 2011 23:20
To: [email protected]
Subject: Re: st: difference between rows
Doug,
Try this:
bysort id: start_date - start_date[_n-1] - date[_n-1]
Chris
On Fri, May 20, 2011 at 11:10 PM, Dougie Elder <[email protected]> wrote:
>
> Apologies if this is quite basic, but I've searched everywhere and I
> cant find the answer !
>
> I have a pile of drug prescription data.
>
> Each patient has several rows of prescriptions e.g.
>
> Id start_date days missed days
> Pt1 10/12/08 21
> Pt1 10/01/09 38
> Pt1 14/03/09 36
> Pt1 15/04/10 36
> Pt2 02/05/09 90
> Pt2 03/06/10 32
>
> I need to calculate the no of days where no drug was available in each
> row of data i.e calculate the difference between 10/12/08 and 10/01/09
> and place the result of ((10/01/09 - 10/12/08)-21 ) at the end of row
> 1
>
> Obviously only for each pt
>
>
> Dougie
>
>
>
>
>
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>
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