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\name{brkdnNest}
\alias{brkdnNest}
\title{Perform a nested breakdown of numeric values}
\description{Breaks down a numeric or categorical element of a data frame
by one or more categorical elements.}
\usage{
brkdnNest(formula,data,maxlevels=10,mct=mean,lmd=std.error,umd=lmd,trueval=NA)
}
\arguments{
\item{formula}{A formula with a numeric element of a data frame on the left and
one or more categorical elements on the right.}
\item{data}{A data frame containing the elements in \samp{formula}.}
\item{maxlevels}{The maximum number of levels in any categorical element. Mainly to
prevent the mess caused by breaking down by a huge number of categories.}
\item{mct}{The measure of central tendency function to use (default is the mean).}
\item{lmd}{The lower measure of dispersion function to use (default is standard
error).}
\item{umd}{The upper measure of dispersion function to use.}
\item{trueval}{The value to use in calculating proportions of a categorical
response variable. See Details.}
}
\value{
A list with four elements:
\item{mctlist}{The list of arrays produced by the function passed as the
\samp{mct} argument.}
\item{lcllist}{The list of arrays produced by the function passed as the
\samp{lmd} argument.}
\item{ucllist}{The list of arrays produced by the function passed as the
\samp{umd} argument.}
\item{barlabels}{A list containing the unique elements of the variables on
the right side of the formula (or the levels if they are factors), in the
order in which they appear in the formula. These will be the default labels
for the \samp{barNest} function.}
This function is similar to \samp{brkdn} in the \pkg{prettyR} package, but
is structured to be used with the \samp{barNest} function. It produces a set
of measures for the overall data, then the subsets of the data defined by
the first variable to the right of the tilde, then the subsets defined by
the first and second variable, and so on.
}
\details{
\samp{brkdnNest} performs a nested breakdown of an element of a data frame
by one or more categorical elements. For each category and optionally
subcategories, the variable on the left of the formula is summarized as
specified by the functions named in \samp{mct}, \samp{lmd} and \samp{umd}.
If \samp{trueval} is not NA, brkdnNest will calculate the proportion of
\samp{trueval} values in the response variable out of the total valid
responses. Remember that \samp{lcllist} and \samp{ucllist} will be
meaningless in this case.
The user should take care when specifying different summary functions.
\samp{barNest} expects a measure of central tendency as the first function
and measures of dispersion as the second and third, if "error bars" are to
be displayed. The user must also decide whether the "error bars" have any
useful meaning.
}
\author{Jim Lemon}
\seealso{\link{by}}
\examples{
test.df<-data.frame(Age=rnorm(100,25,10),
Sex=sample(c("M","F"),100,TRUE),
Marital=sample(c("M","X","S","W"),100,TRUE),
Employ=sample(c("FT","PT","NO"),100,TRUE))
brkdnNest(formula=Age~Sex+Marital+Employ,data=test.df)
}
\keyword{misc}
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