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


From   Tim Evans <Tim.Evans@wmciu.nhs.uk>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: set obs by level (of multiple variables)?
Date   Wed, 23 Jan 2013 11:29:34 +0000

Hi all, further to this, I have another query. When I have generated my duplicate, I wish to change the values of the variables in only one of the duplicated row. At present I am doing this:

bysort TCATOG sex: gen first2 = (_n==1)
expand 2 if first2

Now I want to say, where a duplicate replace the contents of the variables - but I'm struggling as to identify just one of the 'first2' records where first2==1 and not replace the contents of both rows. 

For instance my data (only partially reproduced) look like this:

start	end	n	d	cp_e2		cr_e2		TCATOG2sexfirst2
0	1	442	16	0.9563	1.0079	pTa	Males	1
1	2	426	19	0.9123	1.0093	pTa	Males	0
2	3	407	26	0.8686	0.9924	pTa	Males	0
3	4	381	29	0.8259	0.9642	pTa	Males	0
4	5	352	19	0.7839	0.9611	pTa	Males	0
5	6	333	26	0.7420	0.9361	pTa	Males	0
6	7	307	22	0.7015	0.9192	pTa	Males	0
7	8	285	23	0.6624	0.8949	pTa	Males	0
8	9	262	25	0.6270	0.8552	pTa	Males	0
9	10	237	20	0.5938	0.8268	pTa	Males	0
10	11	217	8	0.5624	0.8408	pTa	Males	0
11	12	209	12	0.5313	0.8390	pTa	Males	0
12	13	197	16	0.5005	0.8183	pTa	Males	0
13	14	181	9	0.4703	0.8274	pTa	Males	0
14	15	172	10	0.4415	0.8302	pTa	Males	0
15	16	162	6	0.4143	0.8520	pTa	Males	0
16	17	156	4	0.3871	0.8884	pTa	Males	0
17	18	152	10	0.3606	0.8883	pTa	Males	0
18	19	130	9	0.3375	0.8701	pTa	Males	0
19	20	77	6	0.3157	0.7956	pTa	Males	0
0	1	442	16	0.9563	1.0079	pTa	Males	1


I wish to change the final row with:
start	end	n	d	cp_e2		cr_e2		TCATOG2sexfirst2
0	0	442	16	1.000		1.000		pTa	Males	1

I can then sort the data according to 'end'

I have four categories of TCATOG2 and both Males and Females.

Best wishes

Tim


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Tim Evans
Sent: 18 January 2013 10:06
To: statalist@hsphsun2.harvard.edu
Subject: RE: st: set obs by level (of multiple variables)?

Thanks Rebecca for your advice - much appreciated.

Best wishes

Tim


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Rebecca Pope
Sent: 17 January 2013 16:31
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: set obs by level (of multiple variables)?

bysort TCATOG sex : gen first2 = (_n==1)

That tests whether it is the first observation or not & returns 1 if true, 0 otherwise.

On Thu, Jan 17, 2013 at 10:24 AM, Tim Evans <Tim.Evans@wmciu.nhs.uk> wrote:
> 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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