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Re: st: Clustered Data Format


From   john metcalfe <johnzmetcalfe@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Clustered Data Format
Date   Tue, 17 Mar 2009 19:27:57 -0700

Thanks so much.
John

On Tue, Mar 17, 2009 at 6:03 PM, Matt Spittal
<Matt.Spittal@cancervic.org.au> wrote:
> Dear John,
>
> The command -reshape- is one way to tackle this problem. The trick that
> often catches me out is the naming of the y variable -- it needs to have a
> number at the end to signify the wave (e.g. y1, y2, ..., yn).
>
> Using your example:
>
>    clear
>    input patientid    y_first    y_second    days_betw
>    299729    0                  0            64
>    295861    0.17               0.08         63
>    292641    0.15               0.5          69
>    end
>
> We then rename the y variable
>
>    rename y_first y1
>    rename y_second y2
>
> And then use the -reshape- command
>
>    reshape long y, i(patientid) j(wave)
>
> Note that you can convert a dataset from long format to wide format with
> -reshape wide-.  Finally, I noticed that you want the variable days_betw to
> be set to zero if this is the first measurement.
>
>    replace days_betw = 0 if wave == 1
>
> See -help reshape- for more information on this command.
>
> -- Matt
> matt.spittal@cancervic.org.au
>
>
> On 18/3/09 11:37 AM, "john metcalfe" <johnzmetcalfe@gmail.com> wrote:
>
>> Dear Statalist,
>> Forgive me if this is too elementary of a question, but I have a
>> longitudinal data set in Format A below upon which I would like to
>> perform linear mixed effects regression (y on days_b grouped by
>> patientid). Is there an easy way to convert the data to Format B?
>> Many thanks,
>> John
>>
>> Format A: (current)
>> patientid y_first y_second days_betw
>> 299729 0                0 64
>> 295861 0.17              0.08 63
>> 292641 0.15               0.5 69
>>
>> Format B: (desired)
>> patientid y days_betw
>> 299729 0 0
>> 299729 0 64
>> 295861 0.17 0
>> 295861 0.08 63
>> 292641 0.15 0
>> 292641 0.5 69
>> *
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>
> *
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