Re: st: RE: Problems with the reshape command

[Syed Basher <syed.basher@yahoo.com>]

In my case, long structure is equally (or better) informative as wide structure. 
In fact, with the wide structure I get numerous empty cells which is visually 
uncomfortable. I guess I will leave the choice between long and wide structure 
to the end-user in my office by supplying them both structures. I appreciate 
Nick's meddling on this matter.

Syed



----- Original Message ----
From: Nick Cox <njcoxstata@gmail.com>
To: statalist@hsphsun2.harvard.edu
Sent: Wed, January 19, 2011 10:19:58 PM
Subject: Re: st: RE: Problems with the reshape command

Rebecca is clearly right in the sense that if you create a
sufficiently fine identifier, -reshape- will oblige. But what is
useful about the data structure created? It rules out as many analyses
as it allows because -line- is arbitrary and separates things you
might want to compare.

But even if this is what Syed is asking for, there is a deeper
question: With this structure, why -reshape- at all? Almost all
analysis questions are easier to answer with a long structure.

Nick

On Wed, Jan 19, 2011 at 5:33 PM, POPE, REBECCA <RPOPE@uams.edu> wrote:
> Hi Syed,
> I'm a bit confused by your use of the term "cross-tab", but since you are using 
>reshape, I'm going to assume you are just trying to get the prices for the 
>different goods to become variables. If so, do you have some other additional 
>identifying variable that you could use in your reshape command? If you have 
>multiple prices for the same item at the same port, might the shipments be from 
>different suppliers or have arrived on different dates? If so, you could use 
>something like the following:
>
> . reshape wide price, i(port date) j(item)
>
> I'm guessing this won't give you exactly what you want because there will still 
>be multiple lines per port (at least if your real data looks like the 
>hypothetical data), but you'll have gotten around reshape's objections and can 
>use other commands to consolidate after that. Other users might have more 
>elegant solutions, but I hope this helps.
>
> If you don't have another logical ID variable to add to port, you can generate 
>a fake one by doing the following:
>
> . by port, sort: generate line = _n
> . reshape wide price, i(port line) j(item)
>
> port   line   pri~1006   pri~2011   pri~2045   pri~4029   pri~4061   pri~7031   
>pri~8041
>------------------------------------------------------------------------------------------
>-
> 1      1          .          .          .          .      92.79          .     
>     .
> 1      2      37.55          .          .          .          .          .     
>     .
> 1      3          .          .      16.21          .          .          .     
>     .
> 2      1          .          .          .          .          .          .     
> 12.55
> 2      2          .      13.13          .          .          .          .     
>     .
>------------------------------------------------------------------------------------------
>-
> 2      3          .      89.68          .          .          .          .     
>     .
> 3      1          .          .          .      27.62          .          .     
>     .
> 3      2          .          .      15.18          .          .          .     
>     .
> 3      3          .          .          .          .          .      68.01     
>     .
> 3      4          .          .          .      15.47          .          .     
>     .
>
>
> Regards,
> Rebecca
>
> Rebecca A. Pope
> Program Manager
> UAMS CCTR Health Services Research
> Fay W. Boozman College of Public Health
> Dept. of Health Policy and Management
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu 
>[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Syed Basher
> Sent: Wednesday, January 19, 2011 10:49 AM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Problems with the reshape command
>
> Dear Statalist,
>
> I am using Stata 11.1.  I have the following hypothetical data:
>
>     +--------------------------+
>      | port       item     price      |
>      |--------------------------|
>  1. |        3    4029   27.62  |
>  2. |        3    4029   15.47  |
>  3. |        1    1006   37.55  |
>  4. |        3    2045   15.18  |
>  5. |        1    2045   16.21  |
>      |------------------------|
>  6. |        1    4061   92.79 |
>  7. |        2    8041   12.55 |
>  8. |        2    2011   89.68 |
>  9. |        3    7031   68.01 |
> 10. |        2    2011   13.13 |
>      |-----------------------|
>
> I would like to reshape the data to wide format using:
> . reshape wide price, i(port) j(item)
>
> This is of course problematic in Stata since "item" is not unique within
> "port".  Eventually I would like to obtain the following cross-tab (in wide
> format):
>
> port |       1006     2011     2045     4029     4061     7031     8041
> -------------------------------------------------------------------
> 1     |        37.55                16.21                 92.79
> 2     |
> 89.68                                                        12.55
> 2     |                   13.33
> 3     |                                15.18     27.62                  68.01
> 3     |                                              15.47
>
> I have been consulting Stata's FAQs on this issue
> (http://www.stata.com/support/faqs/data/reshape3.html) without much success.

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