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\name{annotations}
\alias{annotation}
\alias{annotation,ANY-method}
\alias{annotation,item-method}
\alias{annotation,data.set-method}
\alias{annotation<-}
\alias{annotation<-,ANY,NULL-method}
\alias{annotation<-,ANY,character-method}
\alias{annotation<-,ANY,annotation-method}
\alias{annotation<-,item,annotation-method}
\alias{annotation<-,vector,annotation-method}
\alias{description}
\alias{description,data.set-method}
\alias{description,importer-method}
\alias{description,data.frame-method}
\alias{description,tbl_df-method}
\alias{description<-}
\alias{wording}
\alias{wording<-}
\alias{annotation-class}
\alias{show,annotation-method}
\title{Adding Annotations to Objects}
\description{
Annotations, that is, objects of class \code{"annotation"},
are character vectors with all their elements named.
Only one method is defined for this subclass of character vectors,
a method for \code{\link{show}}, that shows the annotation in
a nicely formatted way. Annotations of an object can be obtained
via the function \code{annotation(x)} and can be set via
\code{annotation(x)<-value}.
Elements of an annotation with names \code{"description"}
and \code{"wording"} have a special meaning.
The first kind can be obtained and set via
\code{description(x)} and \code{description(x)<-value},
the second kind can be obtained via
\code{wording(x)} and \code{wording(x)<-value}.
\code{"description"} elements are used in way the "variable labels"
are used in SPSS and Stata. \code{"wording"} elements of annotation
objects are meant to contain the question wording of a questionnaire
item represented by an \code{"item"} objects.
These elements of annotations are treated in a special way
in the output of the \code{coodbook} function.
}
\usage{
annotation(x)
\S4method{annotation}{ANY}(x)
\S4method{annotation}{item}(x)
\S4method{annotation}{data.set}(x)
annotation(x)<-value
\S4method{annotation}{ANY,character}(x)<-value
\S4method{annotation}{ANY,annotation}(x)<-value
\S4method{annotation}{item,annotation}(x)<-value
\S4method{annotation}{vector,annotation}(x)<-value
description(x)
description(x)<-value
wording(x)
wording(x)<-value
\S4method{description}{data.set}(x)
\S4method{description}{importer}(x)
\S4method{description}{data.frame}(x)
\S4method{description}{tbl_df}(x)
}
\arguments{
\item{x}{an object}
\item{value}{a character or annotation object}
}
\value{
\code{annotation(x)} returns an object of class \code{"annotation"},
which is a named character.
\code{description(x)} and \code{wording(x)} each usually return a character string.
If \code{description(x)} is applied to a \code{\link{data.set}} or an \code{\link{importer}} object,
however, a character vector is returned, which is named after the
variables in the data set or the external file.
}
\examples{
vote <- sample(c(1,2,3,8,9,97,99),size=30,replace=TRUE)
labels(vote) <- c(Conservatives = 1,
Labour = 2,
"Liberal Democrats" = 3,
"Don't know" = 8,
"Answer refused" = 9,
"Not applicable" = 97,
"Not asked in survey" = 99
)
missing.values(vote) <- c(97,99)
description(vote) <- "Vote intention"
wording(vote) <- "If a general election would take place next tuesday,
the candidate of which party would you vote for?"
annotation(vote)
annotation(vote)["Remark"] <- "This is not a real questionnaire item, of course ..."
codebook(vote)
}
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