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# numpy.random.exponential

`numpy.random.``exponential`(scale=1.0, size=None)

  Exponential distribution.

  Its probability density function is

  for `x > 0` and 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 [R193].

  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 [R191], or the time between page requests to Wikipedia [R192].

  Parameters: | scale : float The scale parameter, . size : int or tuple of ints, optional Output shape. If the given shape is, e.g., `(m, n, k)`, then `m * n * k` samples are drawn. Default is None, in which case a single value is returned.

  References

  [R191] | (1, 2) Peyton Z. Peebles Jr., “Probability, Random Variables and Random Signal Principles”, 4th ed, 2001, p. 57.

  [R192] | (1, 2) “Poisson Process”, Wikipedia, http://en.wikipedia.org/wiki/Poisson_process

  [R193] | (1, 2) “Exponential Distribution, Wikipedia, http://en.wikipedia.org/wiki/Exponential_distribution