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Re: st: reshape and overtime variation
From
Nick Cox <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: reshape and overtime variation
Date
Wed, 13 Nov 2013 19:44:32 +0000
This FAQ is also relevant
http://www.stata.com/support/faqs/data-management/listing-observations-in-group/
Nick
[email protected]
On 13 November 2013 19:15, Nick Cox <[email protected]> wrote:
> Suppose you have a bundle of variables, that may or may not be
> constant over time. Then
>
> gen isconstant = .
> gen ismissing = .
>
> foreach v of var <varlist> {
> replace ismissing = missing(`v')
> bysort ismissing panel_id (`v') : replace isconstant = `v'[1] == `v'[_N]
> su isconstant, meanonly
> if r(min) == 1 {
> local NOTFIX `NOTFIX' `v'
> }
> }
>
> If variables are constant, then the first and last are always
> identical after sorting. But you need to segregate missings. (This
> assumes all missings are system missing, not any of .a ... .z.)
>
> Or
>
> foreach v of var <varlist> {
> egen panel_sd = sd(`v'), by(panel_id)
> su panel_sd, meanonly
> if r(min) == 0 {
> local NOTFIX `NOTFIX' `v'
> }
> drop panel_sd
> }
>
> If variables are constant, then their SD will be 0.
>
>
> Nick
> [email protected]
>
>
> On 13 November 2013 18:54, <[email protected]> wrote:
>> Der Stata-list-users,
>>
>> I am working with a balanced panel dataset in long format (that also includes missing values). The dataset has more than 200 variables. Some of these variables vary over time, others do not.
>>
>> I want to reshape the dataset into a wide format without loosing any information. For this purpose I would like to create a local -NOTFIX- which should only contain all variable names of variables that are (within all observation units) constant over time.
>>
>> My ultimate aim is then to type: reshape wide `NOTFIX', i(unit_id) j(year)
>>
>> My question: Can anyone provide a suggestion on how to create NOTFIX?
>>
>> Many thanks!
>> Darjusch Tafreschi
>>
>>
>>
>>
>> *
>> * For searches and help try:
>> * http://www.stata.com/help.cgi?search
>> * http://www.stata.com/support/faqs/resources/statalist-faq/
>> * http://www.ats.ucla.edu/stat/stata/
*
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