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% File src/library/base/man/UseMethod.Rd
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% File src/library/base/man/UseMethod.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 1995-2014 R Core Team
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% Copyright 1995-2022 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{UseMethod}
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\name{UseMethod}
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\title{Class Methods}
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\title{Class Methods}
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\alias{UseMethod}
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\alias{UseMethod}
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\details{
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\details{
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An \R object is a data object which has a \code{class}
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An \R object is a data object which has a \code{class}
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attribute (and this can be tested by \code{\link{is.object}}).
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attribute (and this can be tested by \code{\link{is.object}}).
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A class attribute is a character vector giving the names of
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A class attribute is a character vector giving the names of
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the classes from which the object \emph{inherits}.
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the classes from which the object \emph{inherits}.
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If the object does not have a class attribute, it has an implicit
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If the object does not have a class attribute, it has an
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class. Matrices and arrays have class \code{"matrix"}
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\emph{implicit class}. Matrices and arrays have class \code{"matrix"}
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or\code{"array"} followed by the class of the underlying vector.
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or \code{"array"} followed by the class of the underlying vector.
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Most vectors have class the result of \code{\link{mode}(x)}, except
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Most vectors have class the result of \code{\link{mode}(x)}, except
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that integer vectors have class \code{c("integer", "numeric")} and
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that integer vectors have class \code{c("integer", "numeric")} and
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real vectors have class \code{c("double", "numeric")}.
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real vectors have class \code{c("double", "numeric")}.
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Function \code{\link{.class2}(x)} (since \R 4.0.x) returns the full
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implicit (or explicit) class vector of \code{x}.
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When a function calling \code{UseMethod("fun")} is applied to an
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When a function calling \code{UseMethod("fun")} is applied to an
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object with class attribute \code{c("first", "second")}, the system
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object with class vector \code{c("first", "second")}, the system
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searches for a function called \code{fun.first} and, if it finds it,
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searches for a function called \code{fun.first} and, if it finds it,
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applies it to the object. If no such function is found a function
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applies it to the object. If no such function is found a function
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called \code{fun.second} is tried. If no class name produces a
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called \code{fun.second} is tried. If no class name produces a
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suitable function, the function \code{fun.default} is used, if it
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suitable function, the function \code{fun.default} is used, if it
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exists, or an error results.
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exists, or an error results.
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provided in the \pkg{methods} package.
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provided in the \pkg{methods} package.
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}
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}
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\seealso{
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\seealso{
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The draft \sQuote{R Language Definition}.
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The draft \sQuote{R Language Definition}.
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\code{\link{methods}}, \code{\link{class}},
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\code{\link{methods}}, \code{\link{class}} incl \code{\link{.class2}()};
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\code{\link{getS3method}}, \code{\link{is.object}}.
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\code{\link{getS3method}}, \code{\link{is.object}}.
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}
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}
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\references{
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\references{
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Chambers, J. M. (1992)
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Chambers, J. M. (1992)
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\emph{Classes and methods: object-oriented programming in S.}
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\emph{Classes and methods: object-oriented programming in S.}
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The R Project SVN
R