\HeaderA{power}{Create a Power Link Object}{power}
\keyword{models}{power}
\begin{Description}\relax
Creates a link object based on the link function \eqn{\eta = \mu ^
\lambda}{eta = mu^lambda}.
\end{Description}
\begin{Usage}
\begin{verbatim}
power(lambda = 1)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{lambda}] a real number.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
If \code{lambda} is non-positive, it is taken as zero, and the log
link is obtained.  The default \code{lambda = 1} gives the identity
link.
\end{Details}
\begin{Value}
A list with components \code{linkfun}, \code{linkinv},
\code{mu.eta}, and \code{valideta}.
See \code{\LinkA{make.link}{make.link}} for information on their meaning.
\end{Value}
\begin{References}\relax
Chambers, J. M. and Hastie, T. J. (1992)
\emph{Statistical Models in S.}
Wadsworth \& Brooks/Cole.
\end{References}
\begin{SeeAlso}\relax
\code{\LinkA{make.link}{make.link}},
\code{\LinkA{family}{family}}

To raise a number to a power, see \code{\LinkA{Arithmetic}{Arithmetic}}.

To calculate the power of a test, see various functions in the 
\pkg{stats} package, e.g., \code{\LinkA{power.t.test}{power.t.test}}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
power()
quasi(link=power(1/3))[c("linkfun", "linkinv")]
\end{ExampleCode}
\end{Examples}

