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Re: st: data management question


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: data management question
Date   Sat, 23 Apr 2011 00:56:53 +0100

There is no function -mean()- that will do this. However, David may
well be thinking of -egen- in which case something of the form

egen mean = mean(var11) if inlist(year, 2001, 2002,2003) , by(...)

is a starting point. The transfer of values to 2004 can be
accomplished in various ways. Here are three

1. the argument of mean() is not var11 but

cond(inlist(year, 2001, 2002, 2003), var11, .)

2. ditto but

var11 / inlist(year, 2001, 2002, 2003)

3. follow with

bysort ... (mean) : replace mean = mean[1]

A similar question arose last month

http://www.stata.com/statalist/archive/2011-03/msg01843.html

Nick

On Sat, Apr 23, 2011 at 12:31 AM, Airey, David C
<david.airey@vanderbilt.edu> wrote:
> .
>
> I'm guessing a statement like,
>
> bysort var1-var10 (year): gen mean = mean(var11) if inlist(year,2001,2002,2003)
>
> should get the means for those years for each subset.
>
> Now how to get the 2004 year replaced with the means for each subset?
>
>
>> We have data from 12 schools, grouped into two conditions, for 100 categories, for 9 grades, for each of 10 years. This data is for 20 different variables.
>>
>> We want to replace the scores for year 2004, with the mean of the score for 2001-2003 for each variable, for each grade, for each category, for each condition, for each school. The current values for 2004 are not reliable and so we are making this replacement.
>>
>> How can we do this.
>>
>> Here is an example of the data
>>
>> sch_id group category grade year rex mex sex . . .
>>  1       2     all      3   2001  1   2   0 . . .
>>  1       2     all      3   2002  2   1   1 . . .
>>  1       2     all      3   2003  4   1   1 . . .
>>  2       2     all      3   2004  8   55  6 . . .
>> ...
>>
>> 17       1    blkfem    8   2010  1   2   1 . . .
>>
>> --Alan Acock
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