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Geometric cumulative distribution function


y = geocdf(x,P)
y = geocdf(x,P,'upper')


y = geocdf(x,P) computes the geometric cdf at each of the values in x using the corresponding probabilities in P. x and P 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 P must lie on the interval [0 1].

y = geocdf(x,P,'upper') returns the complement of the geometric cdf at each value in x, using an algorithm that more accurately computes the extreme upper tail probabilities.

The geometric cdf is

where .

The result, y, is the probability of observing up to x trials before a success, when the probability of success in any given trial is p.


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Compute Geometric Distribution CDF

Suppose you toss a fair coin repeatedly. If the coin lands face up (heads), that is a success. What is the probability of observing three or fewer tails before getting a heads?

p = geocdf(3,0.5)
p =

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