\HeaderA{SignRank}{Distribution of the Wilcoxon Signed Rank Statistic}{SignRank}
\aliasA{dsignrank}{SignRank}{dsignrank}
\aliasA{psignrank}{SignRank}{psignrank}
\aliasA{qsignrank}{SignRank}{qsignrank}
\aliasA{rsignrank}{SignRank}{rsignrank}
\keyword{distribution}{SignRank}
\begin{Description}\relax
Density, distribution function, quantile function and random
generation for the distribution of the Wilcoxon Signed Rank statistic
obtained from a sample with size \code{n}.
\end{Description}
\begin{Usage}
\begin{verbatim}
dsignrank(x, n, log = FALSE)
psignrank(q, n, lower.tail = TRUE, log.p = FALSE)
qsignrank(p, n, lower.tail = TRUE, log.p = FALSE)
rsignrank(nn, n)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x,q}] vector of quantiles.
\item[\code{p}] vector of probabilities.
\item[\code{nn}] number of observations. If \code{length(nn) > 1}, the length
is taken to be the number required.
\item[\code{n}] number(s) of observations in the sample(s).  A positive
integer, or a vector of such integers.
\item[\code{log, log.p}] logical; if TRUE, probabilities p are given as log(p).
\item[\code{lower.tail}] logical; if TRUE (default), probabilities are
\eqn{P[X \le x]}{P[X <= x]}, otherwise, \eqn{P[X > x]}{P[X > x]}.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
This distribution is obtained as follows.  Let \code{x} be a sample of
size \code{n} from a continuous distribution symmetric about the
origin.  Then the Wilcoxon signed rank statistic is the sum of the
ranks of the absolute values \code{x[i]} for which \code{x[i]} is
positive.  This statistic takes values between \eqn{0}{} and
\eqn{n(n+1)/2}{}, and its mean and variance are \eqn{n(n+1)/4}{} and
\eqn{n(n+1)(2n+1)/24}{}, respectively.

If either of the first two arguments is a vector, the recycling rule is
used to do the calculations for all combinations of the two up to
the length of the longer vector.
\end{Details}
\begin{Value}
\code{dsignrank} gives the density,
\code{psignrank} gives the distribution function,
\code{qsignrank} gives the quantile function, and
\code{rsignrank} generates random deviates.
\end{Value}
\begin{Author}\relax
Kurt Hornik
\end{Author}
\begin{SeeAlso}\relax
\code{\LinkA{wilcox.test}{wilcox.test}} to calculate the statistic from data, find p
values and so on.

\code{\LinkA{dwilcox}{dwilcox}} etc, for the distribution of \emph{two-sample}
Wilcoxon rank sum statistic.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
require(graphics)

par(mfrow=c(2,2))
for(n in c(4:5,10,40)) {
  x <- seq(0, n*(n+1)/2, length=501)
  plot(x, dsignrank(x,n=n), type='l', main=paste("dsignrank(x,n=",n,")"))
}
\end{ExampleCode}
\end{Examples}

