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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, 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: [email protected]
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.
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package bspline from http://www.imperial.ac.uk/nhli/r.newson/stata10
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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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