[R] rgamma question
Spencer Graves
spencer.graves at pdf.com
Fri Feb 6 00:44:32 CET 2004
Jorge: If I have trouble understanding documentation with
something like this, I make plots, e.g., of dgamma vs. x for different
values for shape and rate or scale.
hope this helps. spencer graves
Peter Dalgaard wrote:
>"Icabalceta, Jorge L." <Icabalceta_j at wlf.state.la.us> writes:
>
>
>
>>I was trying to generate random numbers with a gamma distribution. In R the
>>function is:
>>rgamma(n, shape, rate = 1, scale = 1/rate). My question is that if
>>X~gamma(alpha, beta) and I want to generate one random number where do I
>>plug alpha and beta in rgamma? and, what is the meaning and use of rate?
>>
>>
>
>Well, it depends on your definition of alpha and beta.... You need to
>match up your notation for the gamma density with that given on
>help(rgamma), which will also tell you what to do with them.
>
>The "rate" argument just allows you to specify the scale as its
>inverse. A large rate corresponds to a narrow distribution. I suspect
>this is popular notation for interarrival distributions in queuing
>theory.
>
>
>
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