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From |
Nick Cox <[email protected]> |

To |
"[email protected]" <[email protected]> |

Subject |
Re: st: Multiplicative Functions in Stata |

Date |
Sat, 30 Nov 2013 10:33:12 +0000 |

You don't say why you want to "input" this to Stata. My best guess is that you want to fit this model, for which you need -nl-. Looking at (a+X^b+Y^c+Z^d)[1+exp(u-sum(siTi)-nM)]^(-1) the reciprocation is easier to write as a division. Stata has its own meanings for square brackets, which should become parentheses (a+X^b+Y^c+Z^d)/(1+exp(u-sum(siTi)-nM)) Multiplications must all be explicit (a+X^b+Y^c+Z^d)/(1+exp(u-sum(siTi)-n*M)) and the sum will need to be spelled out (e.g.) (a + X^b + Y^c + Z^d)/(1 + exp(u - s1 * T1 - s2 * T2 - s3 *T3 - n*M)) I will stop there. The -nl- manual entry says more, especially about the brace notation to indicate parameters. -nl- often needs good initial estimates of the parameters to converge at all, as is characteristic of the genre. Nick [email protected] On 30 November 2013 02:57, Justin Hustrulid <[email protected]> wrote: > Hello, > > I have a damage abatement model I've seen in an article that I'm trying to > replicate, but I'm not quite sure how to input it into Stata. I'm using > Stata 12 SE for Windows. > > Here's the function: > > Y=F(Z)G(X) > > Y=(a+X^b+Y^c+Z^d)[1+exp(u-sum(siTi)-nM)]^(-1) > > > > I hope its clear, as I had to retype it since the original was in html. > X,Y, Z, T, and M are independent variables, while the lower case letters > are parameters to be estimated. i is an index, but I can't get it to be > subscript without statalist bouncing the email back to me. The first part > is a straightforward log-log Cobb-Douglass function, but > I'm not sure how to do the part in brackets or how to multiply them > together to get Y. I'm also unsure of whether both parts are done at the > same time or in separate regressions. The article says the G(X) part is > logistic. I'm fairly new to Stata and econometrics in general so any help > in making this regression work would be greatly appreciated. I hope I can > learn a lot from statalist. > > Thanks, > Justin > * > * 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/ * * 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/

**References**:**st: Multiplicative Functions in Stata***From:*Justin Hustrulid <[email protected]>

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