\begin{Schunk}
\begin{Sinput}
 plot(tann ~ elevationP100, data = dat, xlab="Elevation (100s feet)", ylab="Annual Temperature Average")
 abline(mod1)
 newdf <- data.frame(elevationP100 = plotSeq(dat$elevationP100, 20))
 pconf <- predict(mod1, interval = "confidence", newdata = newdf)
 lines(newdf$elevation, pconf[, "lwr"], lwd = 1.5, lty=4, col="red")
 lines(newdf$elevation, pconf[, "upr"], lwd = 1.5, lty=4, col="green")
 legend("topright", legend=c("predicted","lower CI","upper CI"), lty=c(1,4,4), col=c("black", "red","green"), lwd = c(1, 1.5, 1.5))
\end{Sinput}
\end{Schunk}
