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

From   Enzo Coviello <>
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:
If you are using Stata 9, than -stphtest- is out of date and you can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.




*---------- 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 <> 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

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