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From | Christopher Baum <kit.baum@bc.edu> |
To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
Subject | re: re:st: Creating variable based on time reference CORRECTION |
Date | Wed, 19 Oct 2011 17:28:00 -0400 |
<> Correction: pasted the wrong line. Important to make sure data are sorted by date within group. <> Matthew said I have a data set with 3 variables -- "id", "datesubmitted", and "group" -- and 5 observations. id datesubmitted group 1. 1oct2011 1 2. 1aug2011 2 3. 2aug2011 2 4. 5aug2011 2 5. 9oct2011 1 I would like to create a new variable called "responsetime" which reflect the amount of time elapsed (categorically) between the first response and each later observation within a group. For example, if an observation occurred within two days of the first response from that group, it would be a 1; between two and five days, it would be a 2; six and greater would be a 3. In this case, IDs 1 and 5 would have a "responsetime" of 1 and 3, respectively. IDs 2, 3, and 4 would have "responsetime" of 1, 1, and 2, respectively. I'd like to do this across thousands of observations and dozens of groups. Is there a simple way to do this that the trusty Google didn't turn up? g datesubmitted = date(datesub,"MDY") bys group (datesubmitted): g delta = datesubmitted - datesubmitted[1] . l +--------------------------------------+ | datesub group datesu~d delta | |--------------------------------------| 1. | 10/1/2011 1 18901 0 | 2. | 10/9/2011 1 18909 8 | 3. | 8/1/2011 2 18840 0 | 4. | 8/2/2011 2 18841 1 | 5. | 8/5/2011 2 18844 4 | +--------------------------------------+ Kit Baum | Boston College Economics & DIW Berlin | http://ideas.repec.org/e/pba1.html An Introduction to Stata Programming | http://www.stata-press.com/books/isp.html An Introduction to Modern Econometrics Using Stata | http://www.stata-press.com/books/imeus.html Kit Baum | Boston College Economics & DIW Berlin | http://ideas.repec.org/e/pba1.html An Introduction to Stata Programming | http://www.stata-press.com/books/isp.html An Introduction to Modern Econometrics Using Stata | http://www.stata-press.com/books/imeus.html * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/