# problem-9.20

problem-9.20 A plot of both the empirical density and the theoretical density of the gamma distribution with parameters chosen by fitdistr() can be produced as follows:

    > library(MASS)
    > fitdistr(rivers,"gamma")
         shape       rate
      2.5783541   0.0043609
     (0.2489438) (0.0004386)
    ... skip warnings ...
    > plot(density(rivers))
    > x = 0:4000
    > lines(x, dgamma(x,shape=2.578, rate= 0.00436), lty=2)

The gamma shape matches the data, but the tail behavior does not seem that similar. A quantile-quantile plot will show this:

    > qqplot(rivers, rgamma(100,shape=2.578, rate= 0.00436))