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From | Austin Nichols <austinnichols@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: Test for significance of the difference between knee locations? |
Date | Thu, 18 Oct 2012 22:32:07 -0400 |
Joerg Luedicke <joerg.luedicke@gmail.com>: Stata 12 allows you to test coefs that have no corresponding variables in the data; Stata 11 gives an error msg, so you must instead: test _b[k1]==_b[k2] On Thu, Oct 18, 2012 at 6:12 PM, Joerg Luedicke <joerg.luedicke@gmail.com> wrote: > I was just putting together some example code, similar in principle to > Austin's code, but encountered difficulties with the -test- command. > If we use Austin's code: > > *--Austin Nichols' code-- > sysuse nlsw88, clear > *compare extremum positions for quadratics, e.g. for > *tw qfit wage age if union==0||qfit wage age if union==1 > reg wage c.age##c.age##i.union, nohe > loc 1 (k1:-_b[age]/_b[c.age#c.age]/2) > loc 2 (k2:-(_b[age]+_b[1.union#c.age])/ > loc 2 `2'(_b[c.age#c.age]+_b[1.union#c.age#c.age])/2) > nlcom `1' `2', post > test k1==k2 > *------------------------------- > > I get an error message after -test k1==k2-: > > . test k1==k2 > k1 not found > r(111); * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/