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From |
sjsamuels@gmail.com |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: ROC Curve plots |

Date |
Mon, 13 Jul 2009 14:55:58 -0400 |

-- The number of cutpoints is equal to the number of distinct predictions from the model, which is in turn equal to the number of distinct configurations of the predictors. If you have primarily categorical predictors, smoothing may give a false impression of the discriminatory power of the model if the plot is not already smooth-appearing (and then, why smooth?). To get a smoothed plot you can download -senspec-, written by Roger Newson, from SSC. It will output variables for plotting. You might need to add artificial observations at the endpoints of the ROC plot: (0,1) and (1,0). See an example at: http://www.stata.com/statalist/archive/2009-01/msg00689.html. Then use -lowess- or -lpoly- to smooth the plot. -Steve On Mon, Jul 13, 2009 at 10:32 AM, Stephan Rudolfer<stephan.rudolfer@manchester.ac.uk> wrote: > I am working on a database of about 3,000 patients, and wish to plot the ROC curves of various diagnostic algorithms based on logistic regression, using roctab and roccomp. Perhaps unsurprisingly, the plots are very "fuzzy", presumably since the cutpoints generated depend on the total number of patients in the database and hence are too numerous? > > My question: Is it possible to get a "cleaner" ROC curve plot? The roc routines don't seem to allow any control of the number of cutpoints used for the ROCC. > > Many thanks in advance for any help you can provide, > Stephan Rudolfer > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > -- Steven Samuels sjsamuels@gmail.com 18 Cantine's Island Saugerties NY 12477 USA 845-246-0774 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: ROC Curve plots***From:*"Stephan Rudolfer" <stephan.rudolfer@manchester.ac.uk>

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