You should notice that the plots in the top row are exactly the same as those we constructed from “first principles” in Figure 2.3. However, gev.diag also gives a “return level plot” (bottom left) and a plot of the fitted GEV density superimposed onto a histogram of the actual data. The return level plot is really just a quantile plot, but the x-axis is drawn on a logarithmic scale so as the compress the tail of the fitted GEV distribution and thus focus attention on long-period return levels, extrapolated far beyond the range of our observed data. Attached to these return level estimates at 95% confidence bounds using estimate +-1.98*se, where the standard errors have been obtained via the delta method. Superimposed are empirical quantiles for the data we are analyzing, for comparison. Both this plot, and the plot of the data with the fitted density, seem to indicate the adequacy of our fitted GEV.