Calculating the expected number of zeros under Poisson and Negative Binomial distributions in R

问题

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I know the maths, but how to calculate the expected number of zeros under Poisson and Negative Binomial distributions in R? Is there any function to do so?

回答1:

You say you know the mathematics, in which case you already know you're calculating n p(0), right?

You already know n.

So isn't your question "How do I evaluate p(0) = P(X=0) for a Poisson or negative binomial in R?"

Try

?Poisson

and

?NegBinomial

And you will see there's a dpois function for the Poisson, and a similar one for the negative binomial.

So n*dpois(0,lambda) (with whatever value you need in place of lambda) would give the expected number of zeros from a given Poisson distribution. The negative binomial calculation works similarly.

来源：https://stackoverflow.com/questions/22288824/calculating-the-expected-number-of-zeros-under-poisson-and-negative-binomial-dis