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Re: st: plot using -stphtest- answer and new puzzle


From   Enzo Coviello <enzo.coviello@alice.it>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: plot using -stphtest- answer and new puzzle
Date   Sun, 08 Oct 2006 10:41:13 +0200

At 10.13 08/10/2006, you wrote:
Nishant:
If you are using Stata 9, than -stphtest- is out of date and you can
better use -estat phtest-, but that does not answer your question.

You can pile up almost any options you can use after -twoway- after
-estat phtest, plot(varname)- (or -stphtest, plot(varname)-). In your
case you want to change the title on the y-axis, so you can add
ytitle("whatever"). This is illustrated in the example below.

As I understand it, the plot option just shows a scatter plot of scaled
Schoenfeld residuals against time with a lowess smooth fitted through
it. If I do that by hand my lowess smooth is a lot smoother than the
result from -estat phtest-, but the footnote indicates that the same
bandwidth is used. Does anybody have any ideas?

Hi Maartern,

I believe that estat phtest, plot(varname) internally invokes :

lowess ... , mean noweight

i.e. running mean instead of running line and no wheigts.

Often the lowess plot of scaled Shoenf residuals "by hand" looks better than the default plot.

Best

Enzo




HTH,
Maarten

*---------- begin example --------
sysuse cancer, clear
stset studytime, failure(died)
xi: stcox i.drug age, schoenfeld(sch*) scaledsch(sc*)
lowess sc3 _t, ytitle("scaled Schoenfeld - age at interview") name(a)
stphtest, plot(age) ytitle("scaled Schoenfeld - age at interview")
estat phtest, plot(age) ytitle("scaled Schoenfeld - age at interview")
*---------- end example ----------

--- Nishant Dass <nishant_dass@yahoo.com> wrote:
> Could anyone tell me how I could change the titles along
> axes of my plot of scaled Schoenfeld residuals?
>
> I am using "stphtest, plot(myvar)" to get the plot and by
> default, the plot shoes the variable name "myvar" along the
> y-axis while I would to display the label instead.



-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------



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