#### Previous topic

numpy.random.RandomState.dirichlet

#### Next topic

numpy.random.RandomState.f

# numpy.random.RandomState.exponential

`RandomState.``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 [R132].

  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 [R130], or the time between page requests to Wikipedia [R131].

  Parameters : | scale : float The scale parameter, . size : tuple of ints Number of samples to draw. The output is shaped according to size.

  References

  [R130] | (1, 2) Peyton Z. Peebles Jr., “Probability, Random Variables and Random Signal Principles”, 4th ed, 2001, p. 57.

  [R131] | (1, 2) “Poisson Process”, Wikipedia, http://en.wikipedia.org/wiki/Poisson_process

  [R132] | (1, 2) “Exponential Distribution, Wikipedia, http://en.wikipedia.org/wiki/Exponential_distribution