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From | Jennyfer Wolf <jennyfer.wolf@googlemail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: RE: nl-function log4-formula |
Date | Wed, 16 Nov 2011 12:23:08 +0100 |
Dear Nick, thanks for your answer. I tried with the parantheses outside: 2. nl(VAR1={b0}+{b1}/(1+exp(-{b2}*(VAR2-{b3})))) if VAR3=="xxx" It does not change anything. Still I don't get same reults as with log4 and only an estimate for b0. Would you have another idea? Thank you! Jennyfer 2011/11/16 Nick Cox <n.j.cox@durham.ac.uk>: > I don't know, but tucking the -if- condition inside the parentheses looks a bit odd. Try moving it outside. > > -nl- is a command, not a function. > > Nick > n.j.cox@durham.ac.uk > > Jennyfer Wolf > > I am working with the nl-function and with the logistic function model log 4. > Could somebody please explain me why I do not get the same outout if I type: > > 1. nl log4: VAR1 VAR2 if VAR3=="xxx" > > and > > 2. nl(VAR1={b0}+{b1}/(1+exp(-{b2}*(VAR2-{b3}))) if VAR3=="xxx") > > Actually 1. should just be an abbreviation of 2.? > If I run command 1, I get estimates for b0, b1, b2, b3, if I run > command 2 I only get an estimate for b0 and b1-b3 are 0. > > Could somebody explain how to write the formula "in full" (like in > 2.), to get the same results as in the first formula. > > > * > * 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/