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\name{items}
\alias{item}
\alias{items}
\alias{item-class}
\alias{item.vector-class}
\alias{integer.item-class}
\alias{double.item-class}
\alias{numeric.item-class}
\alias{character.item-class}
\alias{datetime.item-class}
\alias{Date.item-class}
\alias{as.item}
\alias{as.item,numeric-method}
\alias{as.item,logical-method}
\alias{as.item,character-method}
\alias{as.item,factor-method}
\alias{as.item,ordered-method}
\alias{as.item,POSIXct-method}
\alias{as.item,Date-method}
\alias{as.item,double.item-method}
\alias{as.item,integer.item-method}
\alias{as.item,character.item-method}
\alias{as.item,datetime.item-method}
\alias{as.item,Date.item-method}
\alias{[,item.vector,numeric,missing,missing-method}
\alias{[,item.vector,logical,missing,missing-method}
\alias{[,datetime.item,numeric,missing,missing-method}
\alias{[,datetime.item,logical,missing,missing-method}
\alias{str.double.item}
\alias{str.integer.item}
\alias{str.character.item}
\alias{str.datetime.item}
\alias{unique,item.vector-method}
\alias{summary,item.vector-method}
\alias{summary,datetime.item-method}
\alias{summary,Date.item-method}
\alias{format,item.vector-method}
\alias{show,item.vector-method}
\alias{format,datetime.item-method}
\alias{format,Date.item-method}
\alias{show,datetime.item-method}
\alias{show,Date.item-method}
\alias{print,item.vector-method}
\alias{print,datetime.item-method}
\alias{print,Date.item-method}
\alias{Compare,numeric.item,character-method}
\alias{Compare,character,numeric.item-method}
\alias{Arith,numeric.item,numeric.item-method}
\alias{Arith,numeric.item,numeric-method}
\alias{Arith,numeric,numeric.item-method}
\alias{Math,numeric.item-method}
\alias{Math2,numeric.item-method}
\alias{Summary,numeric.item-method}
\alias{\%in\%,numeric.item,character-method}
\alias{rep,item.vector-method}
\alias{weighted.mean,item.vector-method}
\title{Survey Items}
\description{
Objects of class \code{item} are data vectors with additional information
attached to them like ``value labels'' and ``user-defined missing values''
known from software packages like SPSS or Stata.
The class \code{item} is intended to facilitate data management of
survey data. Objects in this class should \emph{not} directly used
in data analysis. Instead they should changed into "ordinary" vectors
or factors before. For this see the documentation for \code{\link{as.vector,item-method}}.
}
\usage{
## The constructor for objects of class "item"
## more convenient than new("item",...)
\S4method{as.item}{numeric}(x,
labels=NULL, missing.values=NULL,
valid.values=NULL, valid.range=NULL,
value.filter=NULL, measurement=NULL,
annotation=attr(x,"annotation"), \dots
)
\S4method{as.item}{character}(x,
labels=NULL, missing.values=NULL,
valid.values=NULL, valid.range=NULL,
value.filter=NULL, measurement=NULL,
annotation=attr(x,"annotation"), \dots
)
\S4method{as.item}{logical}(x,\dots)
# x is first coerced to integer,
# arguments in ... are then passed to the "numeric"
# method.
\S4method{as.item}{factor}(x,\dots)
\S4method{as.item}{ordered}(x,\dots)
\S4method{as.item}{POSIXct}(x,\dots)
\S4method{as.item}{double.item}(x,
labels=NULL, missing.values=NULL,
valid.values=NULL, valid.range=NULL,
value.filter=NULL, measurement=NULL,
annotation=attr(x,"annotation"), \dots
)
\S4method{as.item}{integer.item}(x,
labels=NULL, missing.values=NULL,
valid.values=NULL, valid.range=NULL,
value.filter=NULL, measurement=NULL,
annotation=attr(x,"annotation"), \dots
)
\S4method{as.item}{character.item}(x,
labels=NULL, missing.values=NULL,
valid.values=NULL, valid.range=NULL,
value.filter=NULL, measurement=NULL,
annotation=attr(x,"annotation"), \dots
)
\S4method{as.item}{datetime.item}(x,
labels=NULL, missing.values=NULL,
valid.values=NULL, valid.range=NULL,
value.filter=NULL, measurement=NULL,
annotation=attr(x,"annotation"), \dots
)
}
\arguments{
\item{x}{for \code{as.item} methods,
any atomic vector;
for the \code{unique},
\code{summary}, \code{str}, \code{print}, \code{[}, and \code{<-}
methods, a vector with class \code{labelled}.
}
\item{labels}{a named vector of the same mode as \code{x}.}
\item{missing.values}{either a vector of the same mode as \code{x},
or a list with components \code{"values"},
vector of the same mode as \code{x} (which defines individual missing values)
and \code{"range"} a matrix with two rows with
the same mode as \code{x} (which defines a range of missing values),
or an object of class \code{"missing.values"}.
}
\item{valid.values}{either a vector of the same mode as \code{x},
defining those values of \code{x} that are to be considered as valid,
or an object of class \code{"valid.values"}.}
\item{valid.range}{either a vector of the same mode as \code{x} and length 2,
defining a range of valid values of \code{x},
or an object of class \code{"valid.range"}.}
\item{value.filter}{an object of class \code{"value.filter"}, that is, of
classes \code{"missing.values"}, \code{"valid.values"}, or \code{"valid.range"}.}
\item{measurement}{level of measurement; one of "nominal", "ordinal", "interval", or "ratio".}
\item{annotation}{a named character vector,
or an object of class \code{"annotation"} }
\item{\dots}{further arguments, ignored.}
}
\seealso{
\code{\link{annotation}}
\code{\link{labels}}
\code{\link{value.filter}}
}
\examples{
x <- as.item(rep(1:5,4),
labels=c(
"First" = 1,
"Second" = 2,
"Third" = 3,
"Fourth" = 4,
"Don't know" = 5
),
missing.values=5,
annotation = c(
description="test"
))
str(x)
summary(x)
as.numeric(x)
test <- as.item(rep(1:6,2),labels=structure(1:6,
names=letters[1:6]))
test
test == 1
test != 1
test == "a"
test != "a"
test == c("a","z")
test != c("a","z")
test %in% 1:3
test %in% c("a","c")
codebook(test)
Test <- as.item(rep(letters[1:6],2),
labels=structure(letters[1:6],
names=LETTERS[1:6]))
Test
Test == "a"
Test != "a"
Test == "A"
Test != "A"
Test == c("a","z")
Test != c("a","z")
Test %in% c("A","C")
Test %in% c("a","c")
as.factor(test)
as.factor(Test)
as.numeric(test)
as.character(test)
as.character(Test)
as.data.frame(test)[[1]]
}
\keyword{manip}
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