Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
From | Roger Newson <r.newson@imperial.ac.uk> |
To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
Subject | st: New version of -bspline- on SSC |
Date | Thu, 10 Feb 2011 12:29:34 +0000 |
The -bspline- package is described as below on my website. The new version adds an option -base(#)- for the modules -frencurv- and -flexcurv-, allowing the user to specify a reference point whose corresponding reference spline is set to zero. In Stata Version 11, the user can then use the reference spline basis in the design matrix of a regression model, without the -noconst- option, and the parameter corresponding to the base reference spline will then be omitted, the intercept will be the value of the spline at the -base()- reference point, and the parameters corresponding to the other reference splines will be differences between the values of the spline at their reference points and the value of the spline at the -base()- reference point. The modules now also save variable characteristics for the generated splines. The characteristic varname[xvar] is set by bspline, frencurv and flexcurv to be equal to the input X-variable name set by xvar(). The characteristics varname[xinf] and varname[xsup] are set by bspline to be equal to the infimum and supremum, respectively, of the interval of X-values for which the B-spline is non-zero. The characteristic varname[xvalue] is set by frencurv and flexcurv to be equal to the reference point on the X-axis corresponding to the reference spline.
Best wishes Roger -- 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 bspline from http://www.imperial.ac.uk/nhli/r.newson/stata10 --------------------------------------------------------------------------- TITLE bspline: Create a basis of B-splines or reference splines DESCRIPTION/AUTHOR(S) The bspline package contains 3 commands, bspline, frencurv and flexcurv. bspline generates a basis of B-splines in the X-variate based on a list of knots, for use in the design matrix of a regression model. frencurv generates a basis of reference splines, for use in the design matrix of a regression model, with the property that the parameters fitted will be values of the spline at a list of reference points. flexcurv is an easy-to-use version of frencurv, and generates reference splines with equally-spaced knots. frencurv and flexcurv have the additional option of generating an incomplete basis of reference splines, which can be completed by the addition of the standard constant variable used in regression models. The splines are either given the names in the newvarlist (if present), or (more usually) generated as a list of numbered variables, prefixed by the generate() option. Usually (but not always), the regression command is called using the noconst option. Full documentation of the program (including Methods and Formulas) can be found in the ancillary file bspline.pdf, which can be viewed using the Adobe Acrobat Reader. Author: Roger Newson Distribution-date: 08 February 2011 Stata-version: 10 INSTALLATION FILES (click here to install) bspline.ado bspline.sthlp frencurv.ado frencurv.sthlp flexcurv.ado flexcurv.sthlp ANCILLARY FILES (click here to get) bspline.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/