Geometric cumulative distribution function

`y = geocdf(x,p)`

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

`y = geocdf(x,p)`

returns
the cumulative distribution function (cdf) of the geometric distribution
at each value 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 distribution cdf at each value in `x`

,
using an algorithm that more accurately computes the extreme upper
tail probabilities.