\begin{Schunk}
\begin{Sinput}
 rate <- 1
 upper <- 10 
 xvals <- seq(0,upper,by=0.02)
 yvals1 <- dexp(xvals, rate=rate)
 plot (xvals, yvals1, type="l", main="", xlab="x",ylab="probability")
 text(.7*max(xvals), .7*max(yvals1), label=bquote(f(x)==exp(-x)))
\end{Sinput}
\end{Schunk}
