Another possibility is to use the -senspec- package, downloadable from
SSC, to calculate sensitivities and specificities, and then to use
Stata's graphics to make the plot.
If you want to compare 2 ROC areas using a confidence interval for the
difference, instead of just a P-value from a chi-squared test, then you
can use the -somersd- package, also downloadable from SSC, together with
-lincom-. See Newson (2002) for how to do this.
I hope this helps.
Roger
References
Newson R. Parameters behind "nonparametric" statistics: Kendall's tau,
Somers' D and median differences. The Stata Journal 2002; 2(1): 45-64.
Download pre-publication draft from
http://www.imperial.ac.uk/nhli/r.newson/
Roger Newson
Lecturer in Medical Statistics
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute
Imperial College London
Royal Brompton campus
Room 33, Emmanuel Kaye Building
1B Manresa Road
London SW3 6LR
UNITED KINGDOM
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Email: [email protected]
www.imperial.ac.uk/nhli/r.newson/
Opinions expressed are those of the author, not of the institution.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Svend Juul
Sent: 22 April 2007 15:56
To: [email protected]
Subject: Re: st: multiple ROCs on 1 graph
Susan wrote:
I am trying to produce 3 ROC on 1 graph. I am using
roctab ... ...., graph
to generate the plots as I am doing non-parametric analysis. I cannot
seem
to find a way of puuting three plots on q axis. Have attempted addplot
but
no luck so far. Any help would be appreciated.
I am using STATA V9.0 for windows.
---------------------------------------------------------------
If you type:
help roc
you will see descriptions of -roctab-, -roccomp- and -rocgold-.
You need -roccomp-.
Hope this helps
Svend
BTW: You use Stata v9.0. Why don't you update? It is easy, it is free,
it is useful.
________________________________________________________
Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6
DK-8000 Aarhus C, Denmark
Phone, work: +45 8942 6090
Phone, home: +45 8693 7796
Fax: +45 8613 1580
E-mail: [email protected]
_________________________________________________________
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