\begin{Schunk}
\begin{Sinput}
 x <- seq(from=0,to=1,by=0.01)
 y <- 2+exp(0.02*x)+1.2*sin(pi*(2*x))+1.8*cos(4*pi*x)
 plot(x, y, type="l",xlab="x",ylab="",main="")
 text( x[20], y[20], expression(f(x)), pos=1 )
 xss <- seq(0.3, 0.5, by=0.01)
 yss <- 2+exp(0.02*xss)+ 1.2*sin(pi*(2*xss))+ 1.8*cos(4*pi*xss)
 polygon(x=c(xss[1], xss, xss[length(xss)] ), y=c(0, yss, 0), col=gray(0.80))
 xss2 <- seq(0.5, 0.7, by=0.01)
 yss2 <- 2+exp(0.02*xss2)+ 1.2*sin(pi*(2*xss2))+ 1.8*cos(4*pi*xss2)
 polygon(x=c(xss2[1], xss2, xss2[length(xss2)] ), y=c(0, yss2, 0), col=gray(0.70))
 mtext(c("0.3", "0.5","0.7"), 1, line=1, at=c(0.3, 0.5,0.7))
\end{Sinput}
\end{Schunk}
