# numpy.random.mtrand.RandomState.exponential¶

method

RandomState.exponential(scale=1.0, size=None)

Draw samples from an 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 .

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 .

Parameters: 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 * k samples are drawn. If size is None (default), a single value is returned if scale is a scalar. Otherwise, np.array(scale).size samples are drawn. out : ndarray or scalar Drawn samples from the parameterized exponential distribution.

References

  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

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