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From |
Laurent Piet <Laurent.Piet@rennes.inra.fr> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: -nlcom- question |

Date |
Mon, 21 Dec 2009 17:26:07 +0100 |

Thank you Ekrem, In fact, your solution works but it is not exactly what I am looking for.

a = a0 + a1*t b = b0 + b1*t what I get from -nl- looks like: ------------------------------------------------------------------------------ | Robust

-------------+----------------------------------------------------------------

------------------------------------------------------------------------------

------------------------------------------------------------------------------

-------------+----------------------------------------------------------------

------------------------------------------------------------------------------

Any clue ? Thank you in advance, Laurent Ekrem Kalkan a écrit :

Hello, you need to take a particular point of X , for example its mean or minimum or maximum value. You can do this: sum X gen xbar=r(mean) and then insert "xbar" where it is needed in your nlcom formula I hope this is what you asked. Ekrem Kalkan 2009/12/16 Laurent Piet <Laurent.Piet@rennes.inra.fr>:Dear list, I think my problem can be solved with -nlcom- but I have not figured out how to do yet. I use the “function evaluator program” version of the -nl- command to fit a parametric Lorenz curve to observed data. The two parameters ‘a’ and ‘b’ characterizing the functional form of the Lorenz curve are expressed as linear combinations of explanatory variables, say a = a0 + a1*X1 + a2*X2 and b = b0 + b1*X1 + b2*X2. So what I really get from -nl- are the a`i's and b`i's coefficients along with their associated std. err., t and p statistics. Now, I want to compute a third parameter, the Gini coefficient ‘g’, which is a non-linear combination of ‘a’ and ‘b’ involving the Beta function. What I ultimately want to compute are the g`i's, that is, the coefficients measuring the effects of the X`i's (including the constant) on ‘g’, with their associated std. err., t and p. I know how to use -nlcom- to do so when only the constant term is involved (nlcom g0: f(_b[/a0],_b[/b0])), but I couldn’t find how to deal with the explanatory variables X. Any idea would be welcome ! Thanks in advance, Regards, Laurent -- Laurent PIET ---------- INRA, UMR1302 INRA-Agrocampus "Structures et Marchés Agricoles, Ressources, Territoires" 4 allée Adolphe Bobierre | tél. : +33 (0)2.23.48.53.83 CS 61103 | fax. : +33 (0)2.23.48.53.80 F-35011 Rennes cedex | laurent.piet@rennes.inra.fr ---------- http://www.rennes.inra.fr/smart * * 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/

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**References**:**st: -nlcom- question***From:*Laurent Piet <Laurent.Piet@rennes.inra.fr>

**Re: st: -nlcom- question***From:*Ekrem Kalkan <kalkan.ekrem@gmail.com>

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