[R] rgamma with rate as vector

[wcyee]

Hi - I have a question about the following code from Bayesian
Computation with R (Jim Albert).

par(mfrow=c(2,2))
m = 500
alphas = c(5, 20, 80, 400)
for (j in 1:4) {
    mu = rgamma(m, shape=10, rate=10)
    lambda1 = rgamma(m, shape=alphas[j], rate=alphas[j]/mu)
    lambda2 = rgamma(m, shape=alphas[j], rate=alphas[j]/mu)
    plot(lambda1, lambda2)
    title(main=paste('alpha=', alphas[j]))
}


How does the function rgamma work in the instance with the rate
specified as a vector of values?  My understanding is that rgamma
returns m random values from the gamma distribution for a given shape,
rate.  But I don't understand what the resulting lambda1's mean with
many rate values.

Thanks!