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From |
Kit Baum <baum@bc.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: Re: marginal effects |

Date |
Sat, 22 Mar 2008 08:04:40 -0400 |

Do the algebra. To calculate dy/dx you must evaluate the derivative at a particular level of z. If you do

reg y x xz

su z, detail

lincom x + `r(p50)' * xz

will evaluate dy/dx at the median value of z. You can readily evaluate it at other percentiles of z.

Kit Baum, Boston College Economics and DIW Berlin

http://ideas.repec.org/e/pba1.html

An Introduction to Modern Econometrics Using Stata:

http://www.stata-press.com/books/imeus.html

On Mar 22, 2008, at 02:33 , statalist-digest wrote:

I am estimating a regression that has no-lineal (or product of variables) variables in their dependent terms - for example:

regress y x xz

The program Stata doesn't allow logical operators in the command regress (or other equation terms as probit) and for that it is previously necessary to define the variable (for example: gen w = xz). However, if the interest is to calculate marginal effects or elasticities (using mfx or margeff or dprobit) - that procedure invalidates the results because the terms no lineal they are not considered (for example: dy/dx = 1 + z and no 1).

Which the simplest way to solve that problem?

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