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RE: st: Subtracting in Variable by a Group
From
Arya Eskamani <[email protected]>
To
"[email protected]" <[email protected]>
Subject
RE: st: Subtracting in Variable by a Group
Date
Fri, 29 Mar 2013 21:53:23 +0000
Wow...it seems so evident now that I'm actually disappointed in myself :) thank you very much! It worked like a charm.
Arya Eskamani, M.S.
Project Manager
4700 Millenia Blvd | Ste 500 | Orlando, FL 32839
407.367.2880 Phone | 877.313.4412 eFax
www.assist-rx.com | [email protected]
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Nick Cox
Sent: Friday, March 29, 2013 12:16 PM
To: [email protected]
Subject: Re: st: Subtracting in Variable by a Group
Your do-file could consist of
bysort group (date): gen time = date - date[_n-1]
but many Stata users would just type that one command.
Nick
On 29 Mar 2013, at 16:10, Arya Eskamani <[email protected]>
wrote:
> Hello and thank you in advance
>
> I'm attempting to find the difference in days between events within
> different groups. The date is formatted %td (daily). Here's an
> example of my dataset:
>
> group event date
> A 1 08mar2013
> A 2 10mar2013
> A 3 15mar2013
> B 1 10sep2012
> B 2 15sep2012
> C 1 07aug2011
> C 2 23aug2011
> C 3 23aug2011
> C 4 24aug2011
> D 1 25dec2012
> E 1 01jan2013
>
> I want to generate a new variable, say "time" , that calculates the
> difference in days from one event occurring to the next event in
> between the groups. For example, in group A there are 2 days between
> even 1 and event 2 and then 5 days from event 2 to event 3, and
> similarly for others. The example below shows what I'm trying to
> achieve:
>
> group event date time
> A 1 08mar2013 .
> A 2 10mar2013 2
> A 3 15mar2013 5
> B 1 10sep2012 .
> B 2 15sep2012 5
> C 1 07aug2011 .
> C 2 23aug2011 16
> C 3 23aug2011 0
> C 4 24aug2011 1
> D 1 25dec2012 .
> E 1 01jan2013 .
>
> Notice that the time variable is blank for 1st events because there is
> no previous event to subtract from. I've never ran an operation
> within a column before and have been doing this in excel but would
> like to just write a do file on this. Any help is much appreciated.
> Thank you again.
>
>
> Arya Eskamani
>
>
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