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Re: st: Dataset transformation problem


From   Jeph Herrin <[email protected]>
To   [email protected]
Subject   Re: st: Dataset transformation problem
Date   Wed, 27 May 2009 14:17:55 -0400


Something like:

  gen month=mofd(date)
  bys id (date): gen firstmonth=month[1]
  gen period=ceil((month-firstmonth)/6)
  collapse (sum) unit , by(id period)
  reshape wide period, i(id)

?

hth,
Jeph



Josiane Georges wrote:
Hello Fellow Stata Listserv Subscribers:

I have a dataset transformation problem that I could use some guidance
with. I want to collapse a large dataset structured like the example
dataset below to list one observation for each id containing total units
in each 6 month period. I need the dataset to only generate sums for
consecutive months within discreet 6 month periods only. Please note
that each id has a different first month and has observations for a
different set of months.
For example for id 001 it should generate the following observation:

DESIRED RESULT
id	  period1   period2  period3
001      26.4       14.1     17.8

EXAMPLE DATASET
id	  date    units   month
001	01jan2003	3.5	516
001	01feb2003	8.1	517
001	01mar2003	9.0	518
001	01apr2003	5.8	519
001	01may2003	5.5	540
001	01jun2003	8.6	541
001	01jul2003	8.9	552
001	01aug2003	8.9	553
004	01jan2003	4.6	520
004	01feb2003	4.1	521
004	01mar2003	4.6	522
004	01apr2003	4.4	523
004	01may2003	4.6	530
004	01jun2003	4.4	532
004	01jul2003	4.6	540


Josiane "Josie" Georges
Sr. Planning Analyst
Office of Planning
Division of Mental Hygiene
93 Worth Street, Rm 611
New York, NY 10013
Tel: 212-219-5194
Fax: 212-219-5192
Email: [email protected]


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