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st: New version of -bspline- on SSC

From   Roger Newson <[email protected]>
To   "[email protected]" <[email protected]>
Subject   st: New version of -bspline- on SSC
Date   Thu, 20 Jan 2011 13:58:07 +0000

Thanks once again to Kit baum, a new version of the -bspline- package 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 has a new option -labprefix()-, allowing the user to specify the prefix used in the variable labels of the generated splines in the basis. The default is -labprefix("Spline at ")- for the -flexcurv- and -frencurv- modules, and -labprefix("B-spline on ")- for the -bspline- module. Therefore, the splines in the basis have defualt variable labels of the form "Spline at 1760" , but these can be respecified to the form "weight==1760". The second form is similar to the variable labels for the indicator variables produced by -xi-. Reference splines are a generalization of the concept of a set indicator variable to continuous variables (rather than categorical factors), and can be combined (using products) to produce generalized versions of the design matrix variables corresponding to intercepts, differences and interactions. The methods and formulas are explained in a .pdf manual, distribured with -bspline- as an ancillary file.

Best wishes


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
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Email: [email protected]
Web page:
Departmental Web page:

Opinions expressed are those of the author, not of the institution.

package bspline from

      bspline: Create a basis of B-splines or reference splines

      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: 18 January 2011
      Stata-version: 10

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