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From | Roger Newson <r.newson@imperial.ac.uk> |
To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
Subject | st: New version of -somersd- on SSC |
Date | Mon, 20 Jun 2011 18:10:24 +0100 |
The -somersd- package is described as below on my website. The new version adds a new estimation result -e(depvarsum)-, containing the sum, in the estimation sample, of the "dependent variable" specified by -e(depvar)-, which is always the first variable in the input varlist. The result -e(depvarsum)- is useful if this first variable is binary with values 0 and 1, because then -e(depvarsum)- contains the number of observations in which this binary variable is equal to 1.
So, if in the -auto- data you type somersd foreign mpg weight, transf(z) tdist ereturn listthen the Somers' D statistics compare mileage and weight between non-US car models and US car models. The returned result -e(N)- is 74 (the total number of car models), and the returned result -e(depvarsum)- is 22 (the number of non-US car models, in which -foreign- is equal to 1). The number of car models in the smaller of the 2 groups being compared may be a useful diagnostic indicator, indicating how accurate the confidence intervals are. See Newson (2007) for some reasons why this might be the case.
Best wishes Roger ReferencesNewson R. B. Robust confidence intervals for Hodges-Lehmann median differences. 13th UK Stata Users’ Group Meeting, 10–11 September, 2007
Downloadable from the conference website at http://ideas.repec.org/s/boc/usug07.html -- Roger B Newson BSc MSc DPhil 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: r.newson@imperial.ac.uk Web page: http://www.imperial.ac.uk/nhli/r.newson/ Departmental Web page: http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/ Opinions expressed are those of the author, not of the institution. --------------------------------------------------------------------------------- package somersd from http://www.imperial.ac.uk/nhli/r.newson/stata10 --------------------------------------------------------------------------------- TITLE somersd: Kendall's tau-a, Somers' D and percentile slopes DESCRIPTION/AUTHOR(S)The somersd package contains the programs somersd, censlope and cendif,
which calculate confidence intervals for a range of parameters behind rank or "nonparametric" statistics. somersd calculates confidence intervals for generalized Kendall's tau-a or Somers' D parameters,and stores the estimates and their covariance matrix as estimation results.
It can be used on left-censored, right-censored, clustered and/orstratified data. censlope is an extended version of somersd, which also calculates confidence limits for the generalized Theil-Sen median slopes (or other percentile slopes) corresponding to the version of Somers' D
or Kendall's tau-a estimated. cendif is an easy-to-use program to calculate confidence intervals for Hodges-Lehmann median differences(or other percentile differences) between two groups. The somersd package
can be used to calculate confidence intervals for a wide range of rank-based parameters, which are special cases of Kendall's tau-a, Somers' D or percentile slopes. These parameters include differencesbetween proportions, Harrell's c index, areas under receiver operating characteristic (ROC) curves, differences between Harrell's c indices or
ROC areas, Gini coefficients, population attributable risks, median differences, ratios, slopes and per-unit ratios, and the parameters behind the sign test and the Wilcoxon-Mann-Whitney or Breslow-Gehanranksum tests. Full documentation of the programs (including methods and formulas) can be found in the manual files somersd.pdf, censlope.pdf and
cendif.pdf, which can be viewed using the Adobe Acrobat Reader. Author: Roger Newson Distribution-date: 17june2011 Stata-version: 10 INSTALLATION FILES (click here to install) cendif.ado censlope.ado somers_p.ado somersd.ado _bcsf_bisect.mata _bcsf_bracketing.mata _bcsf_regula.mata _bcsf_ridders.mata _blncdtree.mata _somdtransf.mata _u2jackpseud.mata _v2jackpseud.mata blncdtree.mata tidot.mata tidottree.mata lsomersd.mlib cendif.sthlp censlope.sthlp censlope_iteration.sthlp mf_bcsf_bracketing.sthlp mf_blncdtree.sthlp mf_somdtransf.sthlp mf_u2jackpseud.sthlp somersd.sthlp somersd_mata.sthlp ANCILLARY FILES (click here to get) cendif.pdf censlope.pdf somersd.pdf --------------------------------------------------------------------------------- (click here to return to the previous screen) * * 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/