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Re: st: First occurence


From   Joseph McCrary <joe.mccrary@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: First occurence
Date   Thu, 17 May 2007 09:40:12 -0400

sort idcode year
by idcode: egen yrcount=seq()

Then, when yrcount is 1 will be the first year the idcode appears.



Meryle Weinstein wrote:
I've tried following the syntax in FAQ and archives but am having difficulty
with it. I have a dataset that has an idcode and a year for a number of
schools. I want to identify the first year that the idcode appears. I've
tried the following but still don't' get the first occurrence.

by bdsmaster (year), sort: gen noccur = sum(bdsmaster)
by bdsmaster: gen byte first = noccur == 1 & noccur[_n - 1] != noccur

gen byte first = sum(bdsmaster == 1) == 1 & sum(bdsmaster[_n - 1] == 1) ==
0
Thanks for your help.

Meryle Weinstein
Research Scientist
Institute for Education & Social Policy
New York University
Pless Hall
82 Washington Square East, 7th floor
New York, NY 10003
(212) 998-5817
(212) 995-4564 (fax)
www.steinhardt.nyu.edu/iesp



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