\HeaderA{ethanol}{Engine exhaust fumes from burning ethanol}{ethanol}
\keyword{datasets}{ethanol}
\begin{Description}\relax
Ethanol fuel was burned in a single-cylinder engine.  For various
settings of the engine compression and equivalence ratio, the
emissions of nitrogen oxides were recorded.
\end{Description}
\begin{Usage}
\begin{verbatim}ethanol\end{verbatim}
\end{Usage}
\begin{Format}\relax
A data frame with 88 observations on the following 3 variables.
\describe{
\item[NOx] Concentration of nitrogen oxides (NO and NO2) in
micrograms/J.
\item[C] Compression ratio of the engine.
\item[E] Equivalence ratio--a measure of the richness of the air and
ethanol fuel mixture.
}
\end{Format}
\begin{Author}\relax
Documentation contributed by Kevin Wright.
\end{Author}
\begin{Source}\relax
Brinkman, N.D. (1981) Ethanol Fuel---A Single-Cylinder Engine Study of
Efficiency and Exhaust Emissions. \emph{SAE transactions},
\bold{90}, 1410--1424.
\end{Source}
\begin{References}\relax
Cleveland, William S. (1993). \emph{Visualizing Data}.  Hobart Press,
Summit, New Jersey.
\end{References}
\begin{Examples}
\begin{ExampleCode}
## Constructing panel functions on the fly
EE <- equal.count(ethanol$E, number=9, overlap=1/4)
xyplot(NOx ~ C | EE, data = ethanol,
       prepanel = function(x, y) prepanel.loess(x, y, span = 1),
       xlab = "Compression ratio", ylab = "NOx (micrograms/J)",
       panel = function(x, y) {
           panel.grid(h=-1, v= 2)
           panel.xyplot(x, y)
           panel.loess(x,y, span=1)
       },
       aspect = "xy")

# Wireframe loess surface fit.  See Figure 4.61 from Cleveland.
require(stats)
with(ethanol, {
  eth.lo <- loess(NOx ~ C * E, span = 1/3, parametric = "C", 
                  drop.square = "C", family="symmetric")
  eth.marginal <- list(C = seq(min(C), max(C), length.out = 25), 
                       E = seq(min(E), max(E), length.out = 25))
  eth.grid <- expand.grid(eth.marginal)
  eth.fit <- predict(eth.lo, eth.grid)
  wireframe(eth.fit ~ eth.grid$C * eth.grid$E,
            shade=TRUE,
            screen = list(z = 40, x = -60, y=0),
            distance = .1,
            xlab = "C", ylab = "E", zlab = "NOx")
})
\end{ExampleCode}
\end{Examples}

