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st: AW: AW: AW: Error in egen rank(), unique?


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: AW: AW: AW: Error in egen rank(), unique?
Date   Tue, 3 Nov 2009 15:47:15 +0100

<> 

Honestly, I cannot see the point of the problem, but note that your

*************
sort id dbep
by id, sort: egen rank_dbep = rank(dbep), unique
*************

can be telescoped into

-bys id (dbep): egen rank_dbep = rank(dbep), unique-


HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Kaulisch, Marc
Gesendet: Dienstag, 3. November 2009 15:46
An: statalist@hsphsun2.harvard.edu
Betreff: st: AW: AW: Error in egen rank(), unique?

Dear Martin,

Thanks for your answer. Your example works just fine. As it does with a
different dataset. The deletion of the qualifier [_n] does not change the
behaviour.

I found a work around:
The problem was that the var dbep (being formated as %tm) was not ordered.
Dbep1 dbep2 dbep3 dbep4 dbep5
2007m8 2008m5 . 2009m3 .

This sequence was ranked:
1 2 3 3

After inserting
. sort id dbep
Before the 
. by id, sort: egen rank_dbep = rank(dbep), unique
It just works fine

Nonetheless I consider this behaviour as not congruent with the description
of the
Egen rank(), unique function saying "The unique option calculates the unique
rank of exp: values are ranked 1,...,#, and values and ties are broken
arbitrarily.  Two values that are tied for second are ranked 2 and 3. "
(. h egen)

Best regards,


Marc

-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Martin Weiss
Gesendet: Dienstag, 3. November 2009 13:18
An: statalist@hsphsun2.harvard.edu
Betreff: st: AW: Error in egen rank(), unique?


<> 

No problem occur in this code, so where is the material difference to yours?

*************
clear*
set obs 10

gen id=_n
gen dbep1=5+int(10*runiform())
gen dbep2=5+int(10*runiform())
gen deep1=5+int(10*runiform())
gen deep2=5+int(10*runiform())
gen durep1=rnormal()
gen durep2=rnormal()

reshape long dbep deep durep, i(id) j(episode) by id, sort: egen rank_dbep =
rank(dbep), unique by id, sort: egen rank_deep = rank(deep), unique by id,
sort: replace rank_dbep =_n if rank_dbep[_n] == .
sort id rank_dbep
drop episode
reshape wide dbep deep durep rank_deep, i(id) j(rank_dbep)
*************

You do change the values returned by -egen, rank()- with your -replace-
line, so it is hard to argue that -egen- is at fault. Still, the line
clearly intends to replace the rank by its running number if it is missing.
So insert something like -inspect rank_dbep- before that line to see whether
there are any missings in the first place.

Also note that the -if rank_dbep[_n] == .- qualifier could easily be - if
rank_dbep == .-...


HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Kaulisch, Marc
Gesendet: Dienstag, 3. November 2009 11:27
An: statalist@hsphsun2.harvard.edu
Betreff: st: Error in egen rank(), unique?

I have a problem with an egen rank(), unique command (Stata version 10.1).
It looks like it does not produce the unique values as I like.
 
This is my start to rank episodes by their beginning (dbep). First I reshape
the dataset into the long-format.
 
. reshape long dbep deep durep, i(id) j(episode)
 
. by id, sort: egen rank_dbep = rank(dbep), unique . by id, sort: egen
rank_deep = rank(deep), unique
 
. by id, sort: replace rank_dbep = _n if rank_dbep[_n] == .
 
. sort id rank_dbep
 
When I do want to transform this dataset back in the wide format:
 
. drop episode
 
. reshape wide dbep deep durep rank_deep , i(id) j(rank_dbep)
 
I receive the following error:
 
rank_dbep not unique within id;
there are multiple observations at the same rank_dbep within id.
Type "reshape error" for a listing of the problem observations.
r(9);
 
reshape error gives out the number of 15 cases in which rank_dbep is not
unique.
 
Strangely enough with a different dataset the same commands work just fine.
 
Any ideas?
 


Marc Kaulisch

 
iFQ
Institut für Forschungsinformation und Qualitätssicherung Godesberger Allee
90
53175 Bonn, Germany
Tel.: *49 - 228 - 9 72 73 - 25
Fax: *49 - 228 - 9 72 73 - 49
E-mail: kaulisch@forschungsinfo.de
www.forschungsinfo.de

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