\HeaderA{hsv}{HSV Color Specification}{hsv}
\keyword{color}{hsv}
\keyword{dplot}{hsv}
\begin{Description}\relax
Create a vector of colors from vectors specifying hue, saturation and
value.
\end{Description}
\begin{Usage}
\begin{verbatim}
hsv(h = 1, s = 1, v = 1, gamma = 1, alpha)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{h,s,v}] numeric vectors of values in the range \code{[0,1]} for
\dQuote{hue}, \dQuote{saturation} and \dQuote{value} to be combined
to form a vector of colors.  Values in shorter arguments are
recycled.
\item[\code{gamma}] a \dQuote{gamma correction} exponent, \eqn{\gamma}{}
\item[\code{alpha}] numeric value in the range \code{[0,1]} for
alpha transparency channel (0 means transparent and 1 means opaque).
\end{ldescription}
\end{Arguments}
\begin{Value}
This function creates a vector of \dQuote{colors} corresponding to the
given values in HSV space.  The values returned by \code{hsv} can be
used with a \code{col=} specification in graphics functions or in
\code{par}.
\end{Value}
\begin{Section}{Gamma correction}
For each color, \eqn{(r,g,b)}{} in RGB space (with all values in \eqn{[0,1]}{}),
the final color corresponds to \eqn{(r^{\gamma}, g^{\gamma}, b^{\gamma})}{}.
\end{Section}
\begin{SeeAlso}\relax
\code{\LinkA{rainbow}{rainbow}},
\code{\LinkA{rgb}{rgb}},
\code{\LinkA{gray}{gray}}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
hsv(.5,.5,.5)

## Look at gamma effect:
n <- 20;  y <- -sin(3*pi*((1:n)-1/2)/n)
op <- par(mfrow=c(3,2),mar=rep(1.5,4))
for(gamma in c(.4, .6, .8, 1, 1.2, 1.5))
  plot(y, axes = FALSE, frame.plot = TRUE,
       xlab = "", ylab = "", pch = 21, cex = 30,
       bg = rainbow(n, start=.85, end=.1, gamma = gamma),
       main = paste("Red tones;  gamma=",format(gamma)))
par(op)
\end{ExampleCode}
\end{Examples}

