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From |
"Nirina F" <fstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: biprobit and restrictions on RHO |

Date |
Fri, 20 Jul 2007 12:18:00 -0400 |

Thanks a lot Marteen. I will try and let you know. Regrds, Nirina On 7/20/07, Maarten Buis <M.Buis@fsw.vu.nl> wrote:

--- Nirina F wrote: > I know biprobit can just run but can anyone help if I would like to > restrict rho to a value say 0.3 It is possible. You have to know that Stata doesn't maximize with respect to rho, but to the Fisher's Z transformation of rho (also known as the arc-hyperbolic tangent of rho, which is implemented as the -atanh()- function in Stata). So if you want to constrain the rho to be .3, than you have to tell Stata to constrain the appropriate parameter to -atanh(.3)-. The appropriate parameter is the constant in the athrho equation. This is what I have done in the example below (except that I use -.3 instead of .3 as that better fits in this data): *----------- begin example ----------------- use http://www.stata-press.com/data/r9/school.dta, clear local athrho = atanh(-.3) constraint 1 [athrho]_cons = `athrho' biprobit priv vote logptax loginc years, constraint(1) *------------ end example ------------------ (For more on how to use examples I sent to the Statalist, see http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html ) Hope this helps, Maarten ----------------------------------------- Maarten L. Buis Department of Social Research Methodology Vrije Universiteit Amsterdam Boelelaan 1081 1081 HV Amsterdam The Netherlands visiting address: Buitenveldertselaan 3 (Metropolitan), room Z434 +31 20 5986715 http://home.fsw.vu.nl/m.buis/ ----------------------------------------- * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

* * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: RE: biprobit and restrictions on RHO***From:*"Maarten Buis" <M.Buis@fsw.vu.nl>

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