Draw samples from an exponential distribution.
Its probability density function is
x > 0and 0 elsewhere. is the scale parameter, which is the inverse of the rate parameter . The rate parameter is an alternative, widely used parameterization of the exponential distribution .
The exponential distribution is a continuous analogue of the geometric distribution. It describes many common situations, such as the size of raindrops measured over many rainstorms , or the time between page requests to Wikipedia .
- scale : float or array_like of floats
The scale parameter, . Must be non-negative.
- size : int or tuple of ints, optional
Output shape. If the given shape is, e.g.,
(m, n, k), then
m * n * ksamples are drawn. If size is
None(default), a single value is returned if
scaleis a scalar. Otherwise,
np.array(scale).sizesamples are drawn.
- out : ndarray or scalar
Drawn samples from the parameterized exponential distribution.
 Peyton Z. Peebles Jr., “Probability, Random Variables and Random Signal Principles”, 4th ed, 2001, p. 57.  Wikipedia, “Poisson process”, https://en.wikipedia.org/wiki/Poisson_process  Wikipedia, “Exponential distribution”, https://en.wikipedia.org/wiki/Exponential_distribution