Re: st: problem running mfx after glm

[Richard Williams <richardwilliams.ndu@gmail.com>]

At 05:27 PM 8/15/2011, Marlis Gonzalez Fernandez wrote:
> Hello-
>
> Did the following analysis last fall:
>
> glm  ReadingCompCombdiv100 education, family(binomial) link(logit) robust
>
> followed by:
>
> mfx, at(mean)
>
> This provided me with the marginal effects after glm (variable of 
> interest is a proportion).
> Any idea why this is giving me a problem.having trouble figuring out 
> how to do this using margins instead of mfx.
Here is a simple example, that should work in Stata 11 or later:

use "http://www.indiana.edu/~jslsoc/stata/spex_data/ordwarm2.dta";, clear
glm  warmlt3 yr89 male white age ed prst, link(logit) family(binomial) robust
mfx, at(mean)
glm  warmlt3 i.yr89 i.male i.white age ed prst, link(logit) 
family(binomial) robust
margins, dydx(*) atmeans

Note how, the 2nd time around, I added the i. before the names of the 
categorical independent variables. This is necessary so that margins 
will know they are categorical; otherwise it would treat them as 
continuous when computing the marginal effects.
-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
HOME:   (574)289-5227
EMAIL:  Richard.A.Williams.5@ND.Edu
WWW:    http://www.nd.edu/~rwilliam

*
*   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/