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st: New version of -bspline- on SSC


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

Thanks to Kit Baum, a new version of the -bspline- package (described as below on my website) is now available for download from SSC. In Stata, use the -ssc- command to do this, or -adoupdate- if you already have an old version of -bspline-.

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
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