Biostatistics Advance Access published online on October 24, 2006
Biostatistics, doi:10.1093/biostatistics/kxl036
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1 Department of Statistics, Ludwig-Maximilians-Universität München, Akademiestraße 1, 80799 München, Germany
* To whom correspondence should be addressed. In many studies it is known that one or more of the covariates have a monotonic effect on the response variable. In these circumstances, standard fitting methods for generalized additive models (GAM) generate implausible results. A fitting procedure is proposed that incorporates monotonicity assumptions on one or more smooth components within a GAM framework. The algorithm uses the monotonicity restriction for B-spline coefficients and provides componentwise selection of smooth components. Stopping criteria and approximate pointwise confidence bands are derived. The method is applied to data from a study conducted in the metropolitan area of São Paulo, Brazil, where the influence of several air pollutants like SO2 on respiratory mortality is investigated.
Received June 2, 2005
Revised July 27, 2006
Accepted October 20, 2006
Article
Generalized Monotonic Regression Based on B-Splines with an Application to Air Pollution Data
Florian Leitenstorfer 1 * and Gerhard Tutz 1
Florian Leitenstorfer, E-mail: florian.leitenstorfer{at}stat.uni-muenchen.de
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