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Poisson probability density function


Y = poisspdf(X,lambda)


Y = poisspdf(X,lambda) computes the Poisson pdf at each of the values in X using mean parameters in lambda. X and lambda can be vectors, matrices, or multidimensional arrays that all have the same size. A scalar input is expanded to a constant array with the same dimensions as the other input. The parameters in lambda must all be positive.

The Poisson pdf is


The density function is zero unless x is an integer.


A computer hard disk manufacturer has observed that flaws occur randomly in the manufacturing process at the average rate of two flaws in a 4 GB hard disk and has found this rate to be acceptable. What is the probability that a disk will be manufactured with no defects?

In this problem, λ = 2 and x = 0.

p = poisspdf(0,2)
p =

Introduced before R2006a

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