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# RE: st: set obs by level (of multiple variables)?

 From Tim Evans To "statalist@hsphsun2.harvard.edu" Subject RE: st: set obs by level (of multiple variables)? Date Thu, 17 Jan 2013 16:24:24 +0000

Nick thanks for your help. This does what I need, although, rather than duplicating the last record, duplicating the first might be more helpful as this would contain much of the baseline information I already hold. I naively thought that this would work!!:

bysort TCATOG sex : gen first2 = _n - but I have 1-20 rather than 1 followed by 0

I could then use replace first2 = 0 if first !=1 - but I'm assuming there is a better way?

Best wishes

Tim

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: 17 January 2013 15:53
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: set obs by level (of multiple variables)?

The syntax diagram for -set- does not indicate support for -by:- and

1. Whatever is not permitted should be considered forbidden.

2. Less gnomically, there is a really good reason for this. In essence, -set- is about global settings, and even if what you are asking for makes sense -- as it does here -- -set- and -by:- don't mix naturally.

See help for -expand-, -expandcl-, -expandby- (SSC).

bysort stage sex : gen last = _n == _N
expand 2 if last
sort stage sex
... if last

On Thu, Jan 17, 2013 at 3:08 PM, Tim Evans <Tim.Evans@wmciu.nhs.uk> wrote:

> I'm trying to insert extra observations in my dataset - I've calculated survival and wish to graph the results but the data start from less than 100%, but I'd like the graph to graph from time 0 and thus 100%. My dataset is split by gender and stage so I need something that inserts an observation for say males & stage 1, males stage 2, females stage 1 and females stage 2.
>
> Unfortunately, while this will provide me with an observation
>
> set obs `=_N+1' it does not support this:
>
> bysort stage sex: set obs `=_N+1'
>
> Does anyone have an idea how I might do this in Stata 11.2?

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