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| From | Steve Samuels <sjsamuels@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: 1:1 match and identifying result |
| Date | Fri, 27 Apr 2012 08:50:50 -0400 |
Very nice! -cem- from SSC would also allow exact matching on some factors. Steve sjsamuels@gmail.com On Apr 26, 2012, at 6:28 PM, Stas Kolenikov wrote: On Thu, Apr 26, 2012 at 4:17 PM, uniseminar uniseminar <peter.uniseminar@gmail.com> wrote: > Hi all, > > My - beginners - problem concerns the 1:1 matching of a treated group > of companies to an untreated by three variables. Two of the > variables need to be exact matches and one should be in a range of 25% > difference. All numeric: founding year, target year, sales. > my data looks similar to this: > Company1 target-year1 sales1 founding-year ID1 ... > Company1 target-year2 sales2 founding-year ID2 ... > ... > Company2 target-year1 sales1 founding-year IDx+3... > Company2 target-year2 sales2 founding-year IDx+4... > .... > > I tried to work on several matching procedures with merge, vmatch, > psmatch2 nnmatch etc. Neither was suitable for me... > vmatch was matching the three variables, but does not give me the > unique identifier of the matched company next to the treated company. > Further question: If I would receive the ID of the matched comp in the > line of the treated comp(thats the goal), how can I make sure to > compare these two? Something like: if ID of matched is found under > another variable in another line of treated comps then subtract sales > treated from sales matched... > > Hopefully this is understandable...!? Brute force solution that employs the exact equality: sysuse auto ren foreign treated ren mpg year1 ren head year2 replace year2 = 10+2*year2 replace year1 = floor(year1/2) egen same_years = group( year1 year2 ) bysort same_years (price ) : gen byte match_prev = reldif( price, price[_n-1] ) < 0.25 & (treated + treated[_n-1] == 1) bysort same_years (price ) : gen byte match_next = reldif( price, price[_n+1] ) < 0.25 & (treated + treated[_n+1] == 1) list if match_prev == 1 | match_next == 1 , sepby(same) -- Stas Kolenikov, also found at http://stas.kolenikov.name Small print: I use this email account for mailing lists only. * * 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/ * * 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/