RE: st: Plotting the impact of a variable with confidence interval

["Md. Alauddin Majumder" <mm4v@mtmail.mtsu.edu>]

Hi Maarten,
I've just tried the following:

quietly xtreg y c.x##c.x $human_capital $demographic $employment_characteristics $industry $yeardummy $attitude $others if dmale==1 & dwhite==1, fe vce(cl id)
margins, at(x==(15(1)20))

It gives the following output:

Predictive margins                                Number of obs   =       5554
Model VCE    : Robust

Expression   : Linear prediction, predict()

1._at        : x=          15

2._at        : x=          16

3._at        : x=          17

4._at        : x=          18

5._at        : x=          19

6._at        : x=          20

------------------------------------------------------------------------------
             |            Delta-method
             |     Margin   Std. Err.      z    P>|z|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
         _at |
          1  |          .  (not estimable)
          2  |          .  (not estimable)
          3  |          .  (not estimable)
          4  |          .  (not estimable)
          5  |          .  (not estimable)
          6  |          .  (not estimable)
------------------------------------------------------------------------------

Accordingly, the command "marginsplot" gives me a blank diagram. Can you pls provide any suggestions in this regard? Thanks!

Regards
Md. Majumder

________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] on behalf of Maarten Buis [maartenlbuis@gmail.com]
Sent: Monday, March 04, 2013 5:13 AM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Plotting the impact of a variable with confidence interval

On Mon, Mar 4, 2013 at 11:23 AM, Md. Alauddin Majumder wrote:
> I have estimated this regression: y = ax + bx^2+......................................... Now, how can I show the impact of x (considering 20<x<40) on y with a confidence interval in a diagram?

See -help margins- and -help marginsplot-. To use that you need to
include your polynomial terms in factor variable notation, i.e.
-c.x##c.x-, see -help fvvarlist-. Below is an example:

*------------------ begin example ------------------
sysuse nlsw88, clear

gen byte marst = !never_married + married  ///
    if !missing(never_married, married)
label variable marst "marital status"
label define marst 0 "never married"       ///
                   1 "divorced or widowed" ///
                   2 "married"
label value marst marst

gen byte black = race == 2 if race < 3
label variable black "race"
label define black 0 "white" ///
                   1 "black"
label value black black

glm wage c.ttl_exp##c.ttl_exp union grade black i.marst, ///
    link(log) vce(robust) eform

margins , at(ttl_exp=(.12 .5 1/28))
marginsplot, recastci(rarea) ciopts(astyle(ci)) ///
   plotopt(msymbol(i))
*------------------- end example -------------------
(For more on examples I sent to the Statalist see:
http://www.maartenbuis.nl/example_faq )

Also see: <http://www.maartenbuis.nl/wp/inter_quadr/inter_quadr.html>

Hope this helps,
Maarten

---------------------------------
Maarten L. Buis
WZB
Reichpietschufer 50
10785 Berlin
Germany

http://www.maartenbuis.nl
---------------------------------
*
*   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/