\HeaderA{IsPowerOfTwo}{Decides whether vector elements are integral powers of two (returns NA if not).}{IsPowerOfTwo}
\keyword{arith}{IsPowerOfTwo}
\begin{Description}\relax
This function checks to see whether its input is a power of two. If it is then it returns that power otherwise it returns NA.
\end{Description}
\begin{Usage}
\begin{verbatim}
IsPowerOfTwo(n)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{n}] Vector of numbers that are to be checked whether it is a power of two.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
Function takes the log of the input, divides this by log(2) and if the result is integral then it knows the input is true power of two.
\end{Details}
\begin{Value}
If \code{n} is a power of two, then the power is returned otherwise \code{NA} is returned.
\end{Value}
\begin{Section}{RELEASE}
Version 3.6.0 Copyright Guy Nason 1995
\end{Section}
\begin{SeeAlso}\relax
\code{\LinkA{nlevels.default}{nlevels.default}}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
#
# Try and see whether 1,2,3 or 4 are powers of two! 
#
#IsPowerOfTwo(1:4)
# [1]  0  1 NA  2
#
# Yes, 1,2 and 4 are the 0, 1 and 2nd power of 2. However, 3 is not an
# integral power of two.
\end{ExampleCode}
\end{Examples}

