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% File src/library/splines/man/bs.Rd
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% File src/library/splines/man/bs.Rd
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% Part of the R package, https://www.R-project.org
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% Part of the R package, https://www.R-project.org
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% Copyright 1995-2015 R Core Team
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% Copyright 1995-2017 R Core Team
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% Distributed under GPL 2 or later
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% Distributed under GPL 2 or later
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\name{bs}
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\name{bs}
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\alias{bs}
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\alias{bs}
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\title{B-Spline Basis for Polynomial Splines}
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\title{B-Spline Basis for Polynomial Splines}
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\item{x}{the predictor variable. Missing values are allowed.}
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\item{x}{the predictor variable. Missing values are allowed.}
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\item{df}{degrees of freedom; one can specify \code{df} rather than
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\item{df}{degrees of freedom; one can specify \code{df} rather than
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\code{knots}; \code{bs()} then chooses \code{df-degree} (minus one
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\code{knots}; \code{bs()} then chooses \code{df-degree} (minus one
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if there is an intercept) knots at suitable quantiles of \code{x}
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if there is an intercept) knots at suitable quantiles of \code{x}
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(which will ignore missing values). The default, \code{NULL},
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(which will ignore missing values). The default, \code{NULL},
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takes the number of inner knots as \code{length(knots)}. If that is
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corresponds to \emph{no} inner knots, i.e., \code{degree - intercept}.}
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zero as per default, that corresponds to \code{df = degree - intercept}.}
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\item{knots}{the \emph{internal} breakpoints that define the
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\item{knots}{the \emph{internal} breakpoints that define the
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spline. The default is \code{NULL}, which results in a basis for
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spline. The default is \code{NULL}, which results in a basis for
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ordinary polynomial regression. Typical values are the mean or
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ordinary polynomial regression. Typical values are the mean or
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median for one knot, quantiles for more knots. See also
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median for one knot, quantiles for more knots. See also
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\code{Boundary.knots}.}
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\code{Boundary.knots}.}
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\code{knots} and \code{Boundary.knots} are supplied, the basis
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\code{knots} and \code{Boundary.knots} are supplied, the basis
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parameters do not depend on \code{x}. Data can extend beyond
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parameters do not depend on \code{x}. Data can extend beyond
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\code{Boundary.knots}.}
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\code{Boundary.knots}.}
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}
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}
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\details{
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\details{
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\code{bs} is based on the function \code{\link{spline.des}}.
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\code{bs} is based on the function \code{\link{splineDesign}}.
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It generates a basis matrix for
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It generates a basis matrix for
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representing the family of piecewise polynomials with the specified
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representing the family of piecewise polynomials with the specified
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interior knots and degree, evaluated at the values of \code{x}. A
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interior knots and degree, evaluated at the values of \code{x}. A
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primary use is in modeling formulas to directly specify a piecewise
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primary use is in modeling formulas to directly specify a piecewise
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polynomial term in a model.
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polynomial term in a model.
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