Re: st: mfx2 1.1.0 now available

[Richard Williams <Richard.A.Williams.5@ND.edu>]

Kit Baum suggested a couple of clarifications and corrections to my 
announcement about mfx2, so here is the revised version:

Thanks to Kit Baum, a new version of mfx2 is now available from 
SSC.  Type -ssc install mfx2, replace-. It requires Stata 8.2 or 
higher.  The new version now supports the -varlist- option of 
-mfx-.  This can greatly speed up execution time when marginal 
effects are only needed for a few variables.

Here is a more complete description of the program:

mfx2 obtains marginal effects or elasticities after estimation.  It 
is probably most useful after multiple-outcome commands like ologit, 
oprobit, gologit2, slogit, mlogit, oglm, and mprobit but it works 
with other commands as well.

mfx2 offers two key enhancements to Stata's mfx compute command: (a) 
after multiple-outcome estimation commands mfx2 automates the calling 
of mfx and saves the marginal effects for all outcomes in a single 
matrix; and (b) both the model estimates and the marginal effects are 
stored in a way that makes them easy to use with post-estimation 
table formatting commands like Roy Wada's outreg2 and Ben Jann's estout/esttab.

It is important to realize that, if mfx does not work for your 
problem, then mfx2 isn't going to work either.  mfx2 simplifies the 
use of mfx and restructures mfx's output for easier use with table 
formatting programs. But, when it comes to actually estimating the 
marginal effects mfx2 has the same limitations that mfx does.  Other 
marginal effects commands (e.g. margeff, inteff) may be more 
appropriate for your specific purpose.

The following example illustrates mfx2's utility.  The same data and 
variables are analyzed using 4 different categorical data analysis 
models/commands.  By comparing the marginal effects side by side in a 
table created by esttab, you can get a feel for the practical 
differences between the models.  If you tried the same thing using 
mfx, you would have to give 4 times as many mfx commands (one for 
each category of the outcome variable) and it would also be much more 
tedious to get the results into a table.  The -nose- (no standard 
error) and -nolog- options can be used to greatly speed up the 
calculations and unclutter the display (mfx is no speed demon, and 
neither is mfx2).  The most current versions of mfx2, oglm, gologit2, 
and estout (all available from SSC) should be installed for this example.

use "http://www.indiana.edu/~jslsoc/stata/spex_data/ordwarm2.dta";, clear
ologit  warm yr89 male white age ed prst
mfx2, nolog varlist(yr89 male)
oglm  warm yr89 male white age ed prst, het( yr89 male)
mfx2, nolog varlist(yr89 male)
gologit2  warm yr89 male white age ed prst, npl( yr89 male)
mfx2, nolog varlist(yr89 male)
mlogit  warm yr89 male white age ed prst
mfx2, nolog varlist(yr89 male)
esttab ologit_mfx oglm_mfx gologit2_mfx mlogit_mfx, mtitles se nonumbers


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

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