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bundles / numpy 2.4.4 / numpy / random / RandomState / poisson

cython_function_or_method

numpy.random:RandomState.poisson

Signature

def   poisson ( lam = 1.0 ,  size = None )

Summary

Draw samples from a Poisson distribution.

Extended Summary

The Poisson distribution is the limit of the binomial distribution for large N.

Parameters

lam : float or array_like of floats

Expected number of events occurring in a fixed-time interval, must be >= 0. A sequence must be broadcastable over the requested size.

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 lam is a scalar. Otherwise, np.array(lam).size samples are drawn.

Returns

out : ndarray or scalar

Drawn samples from the parameterized Poisson distribution.

Notes

The probability mass function (PMF) of Poisson distribution is

For events with an expected separation the Poisson distribution describes the probability of events occurring within the observed interval .

Because the output is limited to the range of the C int64 type, a ValueError is raised when lam is within 10 sigma of the maximum representable value.

Examples

Draw samples from the distribution: 
import numpy as np
s = np.random.poisson(5, 10000)
✓
Display histogram of the sample: 
import matplotlib.pyplot as plt
count, bins, ignored = plt.hist(s, 14, density=True)
plt.show()
✓
fig-81886212ca1632c0.png
Draw each 100 values for lambda 100 and 500: 
s = np.random.poisson(lam=(100., 500.), size=(100, 2))
✓

See also

random.Generator.poisson

which should be used for new code.

Aliases

  • numpy.random.poisson
  • numpy.random.RandomState.poisson