Can you please help me to generate new variable called - "first_purchase" equal to "1" if it is the first time when a firm (gvkey) has "purchase" = 1 for the first time. Like, in the data sample below gvkey = 001104 will have "purchase" = 0 since in starts having "purchase" = 1 from the beginning of the able data series. Firm = 001109 will have "purchase" = 1 (and 0 otherwise) just in 2005 since this is a day when a firm had its first purchase. Firm 001161 will have "purchase" = 0 since the earliest date available is with contract.
Code:
* Example generated by -dataex-. To install: ssc install dataex clear input str24 gvkey double fyear float purchase "001104" 2001 1 "001104" 2002 1 "001104" 2003 1 "001104" 2004 1 "001104" 2005 0 "001104" 2006 0 "001104" 2007 0 "001104" 2008 0 "001104" 2009 0 "001104" 2010 0 "001104" 2011 1 "001104" 2012 0 "001104" 2013 0 "001104" 2014 0 "001104" 2015 0 "001104" 2016 0 "001104" 2017 0 "001109" 2000 0 "001109" 2001 0 "001109" 2002 0 "001109" 2003 0 "001109" 2004 0 "001109" 2005 1 "001109" 2006 1 "001109" 2007 1 "001109" 2008 1 "001161" 2001 1 "001161" 2002 0 "001161" 2003 0 "001161" 2004 0 "001161" 2005 0 "001161" 2006 1 "001161" 2007 0 "001161" 2008 0 "001161" 2009 0 end
0 Response to Setting a first time appearance of a certain value in the data
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